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Full text of "TM 11-5820-256-10"

DEPARTMENT OF THE ARMY TECHNICAL MANUAL 



TM 11-5820-256-10 



OPERATOR'S MANUAL 



RADIO SET 
AN/GRC-26D 



This copy is a reprint which includes current 
pages from Changes 1 through 4. 



HEADQUARTERS, DEPARTMENT OF THE ARMY 
JUNE 1969 



WARNING 



DANGEROUS VOLTAGES EXIST IN THIS EQUIPMENT 

Be careful when working on the power supply circuits, on the 1 15-volt ac line connections, or on the 240- 
volt plate circuits in Receiver, Radio R-390 (*)/URR. Observe safety precautions when working on the 
transmitting antenna or the transmitting antenna terminals because high radio-frequency voltages exist at 
these points. 

DON'T TAKE CHANCES! 
EXTREMELY DANGEROUS VOLTAGES EXIST IN THE FOLLOWING UNITS: 



Transmitter, Radio T-368 (*)/URT 2,400-volt circuits 

Converter, Frequency Shift CV-1 1 6 (*)/URR 620-volt circuits 

WARNING 
VENTILATION 

The shelter must be ventilated when occupied. Be sure the vents, window shutters, or door is open when 
the equipment is operated. Keep the shelter air intake fan closed during the transportation. The truck 
exhaust stack is near the air intake vent, and there is danger of carbon monoxide poisoning. When the 
vehicle is moving, adequate air circulation exists through the shelter windows. 

WARNING 
ANTENNAS 

Operator and maintenance personnel should be familiar with the requirements of TB SIG 291 before 
attempting installation or operation of the equipment covered in this manual. Failure to follow requirements 
of TB SIG 291 could result in injury or DEATH. 



TM 11-5820-256-10 

WARNING 
RADIATION HAZARD 

A.* 




RADIOACTIVE MATERIAL 
CONTROLLED DISPOSAL REQUIRED 
ACCOUNTABILITY NOT REQUIRED 
STD RW--2 

Audio level meter Ra 226 0.69uCi 

Audio level meter Ra 226 0.40uCi 

Electron Tube CC3W 
Sylvania Co 60 "I.OuCi 

Electron Tube OA2WA 

EEVC U238 O.luCi 

CBS Hytron Ni 63 0.5uCi 

Raytheon Co 60 0.2uCi 

Electron Tube OA2WA 

EEVC U238 O.luCi 

CBS Hytron Ni 62 0.5uCi 

Raytheon Co 60 0.2uCi 

Radiation Hazard Information: The following radiation hazard information must be read and understood by all personnel 

before operating or repairing Radio Set AN/GRC-26D. Hazardous radioactive materials are present in the above listed 

components of the MD-239A/GR, R-290/URR, C-632/GRC-10, R-125/GRC10, and T-235/GRC10. 

The components are potentially hazardous when broken. See qualified medical personnel and the local Radiological 

Protection Officer (RPO) immediately, if you are exposed to or cut by broken components. First aid instructions are 

contained in TB 43-01 1 6, TB 43-01 22, and AR 7551 5. 

NEVER place radioactive components in your pocket. 

Use extreme care NOT to break radioactive components while handling them. 

NEVER remove radioactive components from cartons until you are ready to use them. 



6625-00-669-0769 
6625-00-669-0770 

5960-00-1880968 

5960-00-503-4880 



Change 3 



TM 11-5820-256-10 



If any of these components are broken, notify the local RPO immediately. The RPO will survey the immediate area for 
radiological contamination and will supervise the removal of broken components. 
The above listed radioactive components will not be repaired or disassembled. 

Disposal of broken, unserviceable, or unwanted radioactive components will be accomplished in accordance with the 
instructions in AR 755-15. 



TM 11-5820-256-10 




+ 



SAFETY STEPS TO FOLLOW IF SOMEONE 
IS THE VICTIM OF ELECTRICAL SHOCK 



DO NOT TRY TO PULL OR GRAB THE INDIVIDUAL 



IF POSSIBLE, TURN OFF THE ELECTRICAL POWER 



IF YOU CANNOT TURN OFF THE ELECTRICAL 
POWER, PULL, PUSH OR LIFT THE PERSON TO 
SAFETY USING A DRY WOODEN POLE OR A DRY 
ROPE OR SOME OTHER INSULATING MATERIAL 



SEND FOR HELP AS SOON AS POSSIBLE 



AFTER THE INJURED PERSON IS FREE OF 
CONTACT WITH THE SOURCE OF ELECTRICAL 
SHOCK, MOVE THE PERSON A SHORT DISTANCE 
AWAY AND IMMEDIATELY START ARTIFICIAL 
RESUSCITATION 



TM 11-5820-256-10 

FIXED OPERATION WITH LONG RANGE ANTENNAS 
WARNING 




TELESCOPING TYPICAL TOWER EXTENDED RANGE DOUBLET ANTENNA 
ANTENNA MAST ANTENNA 



NEVER ERECT THESE LONG RANGE ANTENNAS DIRECTLY UNDER POWERLINES. 

IF YOU MUST ERECT THESE LONG RANGE ANTENNAS NEAR POWERLINES, POWERLINE POLES OR TOWERS. 
OR BUILDINGS WITH OVERHEAD POWERLINE CONNECTIONS, NEVER PUT THE ANTENNA CLOSER THAN TWO 
TIMES THE ANTENNA HEIGHT FROM THE BASE OF THE POWERLINE, POLE, TOWER OR BUILDINGS. 

NEVER ATTEMPT TO ERECT ANY LONG RANGE ANTENNA WITHOUT A FULL TEAM. 

BEFORE ERECTING ANY LONG RANGE ANTENNA, INSPECT ALL THE PARTS MAKING UP THE ANTENNA KIT. DO 
NOT ERECT THE ANTENNA IF ANY PARTS ARE MISSING OR DAMAGED. 

DO AS MUCH OF THE ASSEMBLY WORK AS POSSIBLE ON THE GROUND. 

WHEN ERECTING THE ANTENNA, ALLOW ONLY TEAM PERSONNEL IN THE ERECTION AREA, 

MAKE SURE THAT THE AREA FOR THE ANCHORS IS FIRM. IF THE GROUND IS MARSHY OR SANDY, GET 
SPECIFIC INSTRUCTIONS FROM YOUR CREW CHIEF OR SUPERVISOR ON HOW TO REINFORCE THE 
ANCHORS, 

WHEN SELECTING LOCATIONS FOR ANCHORS, AVOID TRAVELED AREAS AND ROADS. IF YOU CANNOT AVOID 
THESE AREAS, GET SPECIFIC INSTRUCTIONS FROM YOUR SUPERVISOR AS TO WHAT CLEARANCE YOUR GUY 
WIRES AND ROPES MUST HAVE OVER THE TRAVELED AREAS AND ROAD. 

CLEARLY MARK ALL GUY WIRES AND ROPES WITH THE WARNING FLAGS OR SIGNS SUPPLIED BY YOU UNIT. 
IN AN EMERGENCY, USE STRIPS OF WHITE CLOTH AS WARNING STREAMERS. 

IF YOU SUSPECT THAT POWERLINES HAVE MADE ACCIDENTAL CONTACT WITH YOUR ANTENNA, STOP 
OPERATING, ROPE OFF THE ANTENNA AREA, AND NOTIFY YOUR SUPERIORS. 

IF THE WEATHER IN YOUR AREA CAN CAUSE ICE TO FORM ON YOUR LONG RANGE ANTENNA AND ITS GUY 
WIRES AND ROPES, ADD EXTRA GUYS TO SUPPORT THE SYSTEM. ROPE OFF THE AREA AND POST IT WITH 
WARNING SIGNS LIKE BEWARE OF FALLING ICE. 

DO NOT TRY TO ERECT ANY ANTENNA DURING AN ELECTRICAL STORM. 

KEEP A SHARP EYE ON YOUR ANCHORS AND GUYS. CHECK THEM DAILY AND IMMEDIATELY BEFORE AND 
AFTER BAD WEATHER. 



TM 11-5820-256-10 

WARNING 



SERIOUS INJURY OR EVEN DEATH CAN HAPPEN IF THE FOLLOWING ARE NOT CAREFULLY 
OBSERVED WHEN INSTALLING AND USING THE ANTENNAS USED WITH YOUR RADIO SETS, 



BEFORE ANY 
MISSION FIND 
OUT 



1 . ARE THERE ANY POWERLINES IN YOUR AREA OF OPERATION ? 

2. HIGH ARE THESE POWERLINES ? 

3. HOW TALL ARE THE POLES OR TOWERS CARRYING POWERLINES ? 



MOBILE OPERATION WITH WHIP ANTENNAS 




DO NOT STOP YOUR VEHICLE UNDER POWERLINES. 

• IF POSSIBLE, TRY TO MAINTAIN MOBILE COMMUNICATIONS WITH YOUR ANTENNA(S) TIED 
DOWN, 

• MAKE SURE AN ANTENNA TIP CAP IS SECURELY TAPED ON THE END OF EACH WHIP ANTENNA. 

• DO NOT LEAN AGAINST OR TOUCH A WHIP ANTENNA WHILE THE TRANSMITTER IS ON, 

• DURING CROSS-COUNTRY OPERATION, DO NOT ALLOW ANYONE TO STICK AN ARM, LEG OR 
WEAPON OVER THE SIDES OF THE VEHICLE, IF YOUR ANTENNA ACCIDENTALLY TOUCHES A 
POWERLINE AND A LEG, ARM OR WEAPON CONTACTS A DAMP BUSH OR THE GROUND, A 
SERIOUS OR FATAL ACCIDENT CAN HAPPEN. 



• IF YOU ARE NOT SURE THAT AN ANTENNA ON YOUR VEHICLE WILL CLEAR A POWERLINE, STOP 
BEFORE YOU GET CLOSE TO THE POWERLINE AND EITHER CAREFULLY TIE DOWN THE 
ANTENNA OR REMOVE ANTENNA SECTIONS TO MAKE SURE THAT YOU CAN SAFELY DRIVE 
UNDER THE POWERLINE. 



TM 11-5820-256-10 



Technical Manual 
No. 11-5820-256-10 



} 



I Chapter 


1 




m 




m 


Section 




I Chapter 


4.| 




m 


Section m 




m 


I Appendix 


A 



El 

Section Q] 



Operator's Manual 
RADIO SET AN/GRC-26D 



HEADQUARTERS 
DEPARTMENT OF THE ARMY 
Washington, D. O, 19 June 1969 



Paragraph Page 
T^30l 



I 2-1-2-101 



3-1-3-4 



3^3~16 



4-11-4-91 



I Indexl 



INTRODUCTION 

INSTALLATION 

OPERATING INSTRUCTIONS 

Operator's controls and indicators 

Operation 

MAINTENANCE INSTRUCTIONS 

SHIPMENT AND LIMITED STORAGE AND DEMOLITION TO PREVENT ENEM Y USE 

Shipment and limited storage I 5-11,5-21 

Demolition of materiel to prevent enemy use I 5-31,5-41 

REFERENCES 

BASIC ISSUE ITEMS LIST (BIIL) AND ITEMS TROOP INSTALLED OR AUTHORIZED 

LIST (ITIAL) 

Introduction 

Basic issue items list 

Items troop installed or authorized list 



Q3 



3-1 



3-7 



4-1 



5-1 



5-1 



A-1 







"This manual supersedes TM 1 1 -5820-256-1 0, 20 July 1 961 , Including all changes. 

Change 1 i 



TM 11-5820-256-10 




TM 11-5805-356-12 




CHAPTER 1 
INTRODUCTION 



TM 11-5820-256-10 



1-1. Scope 

a. T his manual describes Radio Set AN/GRC-26D 
ff ig . 1-11 and covers its installation, operation, and 
operator's maintenance. It includes operation under 
usual conditions, as well as operation with security 
equipment; cleaning and inspection of equipment; and 
replacement of the parts available to the operator 
Detailed discussion of Modulator, Radio MD239(*)/GR 
Switch Box SA-331/U; Control, Radio Set C-1123/GRC 
and Control, Remote Switching C1474/GRC is provided. 
Detailed information pertaining to the remainder of the 
major components comprising Radio Set AN/ GRC-26D 
is contained in the technical manuals listed in lappendixl 

b. Official nomenclature followed by (*) is used to 
indicate all models of the equipment. The chart below is 
a list of such equipments discussed in this manual. 



Nomenclature 



Models represented 



Receiver, Radio R-390(*)/ 
URR. 

Mast Bracket MP-50--O 

Converter, Frequency Shift 
CV-116(*)/URR 

Loudspeaker Assembly 

LS-206O/U. 
Reperforator-Transmitter, 

Teletypewriter TT-76 

O/GGC. 
Teletypewriter TTf-98 

H/FG 

Cabinet, Storage CY-1721 

(*)/GRC. 
Mast AB-155(')/U 



R-390/URR, R-390A/URR 

. MP-50, MP-50-A 
CV-116/URR, CV-1 16A/URR, 

CV-1 16B/URR, CV- 
116C/URR. 
LS-206/U, LS-206A/U 

TT-76/GGC, TT-76A/GGC, 
TT-76B/GGC. 

TT-98/FG, TI98A/FG, TT- 

98B/FG. 
CY-1721/GRC, CY-1721A/GRC 

.AB-155/U, AB155A/U.AB- 
155B/U. 

Modulator, Radio MD MD-239 GR, MD-239A/GR 

239(*)/GR. 

Transmitter, Radio T-368 T-368/URT, T-368A/URT, T- 

368B/ 

(*)/URT. URT, T-368C/URT, T- 

368D/URT, 

T-368E/URT, T-368F/URT. 

Microphone M-29(*)/U M-29/U, M-29A/U 

Shelter, Electrical Equipment S-56A/G, S-56B/G 
S-56(*)/G. 

Mast Section MS-44-(*) MS-44, MS44:A 

Guy MX-381 (')/GRA4 MX-381/GRA-4, MX-381A/GRA-4. 

Guy MX-382(*)/GRA-4 MX-382/GRA-4, MX-382A/GRA-4. 

Guy MX-383(*)/GRA-4 MX-383/GRA-4, MX-51 6A/GRA-4. 

Halyard MX-51 6(*)/GRA-4 MX-515/GRA-4, MX-51 6A/GRA-4. 



1-2. Indexes of Publications 

a. DA Pam 310-4. Refer to the latest issue of DA 
Pam 310-4 to determine whether there are new editions, 
changes, or additional publications pertaining to this 
equipment. 

b. DA Pam 310-7. Refer to DA Pam 310-7 to 
determine whether there are modification work orders 
(MWO's) pertaining to the equipment. 

1-3. Forms and Records 

a. Reports of Maintenance and Unsatisfactory 
Equipment. Maintenance forms, records, and reports 
which are to be used by maintenance personnel at all 
maintenance levels are listed in and prescribed by TM 
38-750. 

b. Report of Packaging and Handling Deficiencies. 
Fill out and forward DD Form 6 (Packaging Improvement 
Report) as prescribed in AR 70058/NAVSUPINST 
4030.29/AFR 71-13/MCO P4030.29A, and DLAR 
4145.8. 

c. Discrepancy in Shipment Report (DISREP) (SF 
361). Fill out and forward Discrepancy in Shipment 
Report (DISREP) (SF 361) as prescribed in AR 55- 
38/NAVSUPINST 4610.53B/AFR 75-18/MCO 
P4610.19C, DLAR 4500.15. 

1-3.1. Reporting of Errors 

The reporting of errors, omissions, and 
recommendations for improving this publication by the 
individual user is encouraged. Reports should be 
submitted on DA Form 2028 (Recommended Changes 
to Publications and Blank Forms) and forwarded direct to 
Commander, US Army Communications and Electronics 
Materiel Readiness Command, ATTN: DRSEL-ME-MQ, 
Fort Monmouth, NJ 07703. 

1-3.2. Administrative Storage 

Administrative storage of equipment issued to and used 
by Army activities shall be in accordance with TM 740- 
90-1. 

1-3.3. Destruction of Army Electronics Materiel 

Destruction of Army electronics materiel to prevent 
enemy use shall be in accordance with TM 750-244-2. 

1-3.4. Reporting Equipment Improvement 
Recommendations (EIR) 

EIR's will be prepared using Standard Form 368 (Quality 
Deficiency Report). Instructions for preparing EIR's are 
provided in TM 38-750, the Army Maintenance 
Management System. EIR's should be 



Change 4 1-1 



TM 11-5820-256-10 



mailed direct to Commander, US Army Communications 
and Electronics Materiel Readiness Command, ATTN: 
DRSEL-ME-MQ, Fort Monmouth, NJ 07703. A reply will 
be furnished direct to you. 

1-4. Purpose and Use 

a. Purpose. Radio Set AN/GRC-26D |(fiq. 1-1) is a 
self-contained radio-teletypewriter station operating over 
a frequency range of 1 .5 to 20.0 megahertz (MHz) with a 
power output of approximately 450 watts. The AN/GRC- 
26D provides facilities for transmission and reception of 



frequency-shift keying (fsk), amplitude-modulated (am.) 
voice, continuous-wave (cw), and combination 
frequency-shift keying and amplitude-modulated (fsk- 
am.) signals. Facilities are also provided for operation 
with security equipment. Normally, am. voice or cw 
service is used only in an emergency or when operating 
conditions prevent the use of the fsk facilities. Voice 
communication may be superimposed upon an fsk signal 
without modifying. 



1-2 



TM 11-5820-256-10 

1-5.1. Items Comprising Operable Radio Sets AN/GRC-26D (FSN 5815-518-0399), and AN/GRC-26D modified by 

M WO 11-5820-256-35/1 



FSN. 



QUANTITY 



AN GRC-26D 



AN/GRC-26D 
with MWO 



Nomenclature, part No., and mfr code 



5815- 
3895- 
4140- 
5820- 
5820- 
5820- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 

5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5885- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5995- 
5340- 
5935- 
5935- 
5935- 
5935- 
5935- 
5820- 
5820- 
5820- 



082-3868 
356-3937 
347-6807 
404-271 8 
497-8596 
503-0951 
519-1146 
889-0751 
823-2974 
752-1362 
752-2056 
636-3329 
170-8780 

752-2335 
1 70-7929 
823-2012 
349-4844 
903-7725 
752-2139 
510-0615 
752-251 1 
926-0772 
926-0774 
926-0775 
926-0773 
926-0831 
926-0818 
999-0116 
926-0819 
926-0807 
926-0817 
926-0836 
926-0833 
999-2650 
999-2649 
926-0835 
286-2491 
259-0019 
201-2410 
204-8382 
201-2735 
259-0099 
537-3847 
082-3950 
503-3468 



5995-889-1314 
5995-523-1789 
5995-538-9764 
5995-752-2135 
6145-283-9634 
5995-164-7716 



1 
1 
1 
1 
1 
1 

1 
1 
2 
1 
2 
2 
1 
2 
2 
1 
2 
1 
2 
1 



3 
2 
2 



2 
2 
1 
2 



NOTE 

The part number is followed by the applicable 5-digit Fideral supply 
code for manufacturers (FSCM) identified in SB 708-42 and used to 
identify manufacturer, distributor, or Government agency, etc. 
Modification Kit: For AN/GRC-26D 
Axle, RL-27D 

Blower Assembly, Electrical HD-223/G 
Bracket MP-50-A 
Bracket MT-657/GRC 
Cabinet, Electrical, CY-1807/G 

Cable Assembly, Power, Electrical: (5 ft 5 in) SC-C-7548A; 80063 

Radio Frequency CG-409/G: (3 ft in.) 

Radio Frequency CG409G/U: (8 ft) 
Radio Frequency CG-629A/U: (75 ft) 
Radio Frequency CG-718A/U: (8 ft) 
Radio Frequency CG-718A/U: (25 ft 6 in) 
Special Purpose Electrical CX-1200: (3 ft 9 in) 
Special Purpose, Electrical CX-1201/U: (5 ft 2 in) 
Radio Frequency CG-1 333/U: (4 ft) 
Power Electrical CX-1 166/U: (50 ft) 
CG-1334/U: (500 ft) 

Special Purpose, Electrical CX-1852/U: (6 ft) 
Power Electrical CX-2254/U: (10 ft) 
Special Purpose CX-3267/U: (12 ft 6 in.) 
Special Purpose CX-3268/U: (14 ft) 
Power Electrical CX-6485/U: (12 ft 6 in.) 
Special Purpose, Electrical CX-9994A/U: (3 ft) 
Special Purpose 
Special Purpose 
Special Purpose 
Special Purpose 
Special Purpose 
Special Purpose 



Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 
Cable Assembly 



Electrical CX-9995A/U: (3 ft in.) 
Electrical CX-9995A/U: (8 ft 6 in.) 
Electrical CX-9996A/U: (10 ft) 
Electrical CS-9997A/U: (8 ft 6 in.) 
Electrical CX-9998/U: (8 ft 6 in.) 
Electrical CX-1 141 1/U: (8 ft 6 in.) 
Special Purpose, Electrical CX-1 1 41 2: (1 8 ft 1 in.) 
Special Purpose, Electrical CX-1 1413: (8 ft 6 in.) 
Special Purpose, Electrical CX-1 1414/U: (8 ft 6 in.) 
Special Purpose, Electrical CX-11415/U: (2 ft 6 in.) 
Special Purpose, Electrical CX-11415/U: (6 ft 6 in.) 
Special Purpose, Electrical CX-11416/U: (10 ft) 
~ ''" Electrical CX-1 1417: (35 ft in.) 

Electrical CX-1 141 8: (8 ft 6 in.) 



Special Purpose 
Special Purpose 
Clamp, Loop: SC-B-19491 ; 80063 
Connector, Adapter, UG-643/U 
Connector, Adapter, UG-971 /U 
Connector, Adapter, UG-27C/U 
Connector, Adapter, UG-567A/U 
Connector, Adapter, UG-637/U 
Control, Radio Set C-1123/GRC 
Control, Radio Set C-1 1 23/URC (Modification Kit) 
Control, Remote, C-1474/GRC 

Control, Remote Switching C-1474/GRC: (Modification Kit) 

CordCG-55E/U: (3 ft 4 in.) 

Cord Assembly, Electrical CX-3296/U: (13 ft 6 in.) 

Cord Assembly, Electrical CX-3270/U: (5 ft) 

Cord Assembly, Electrical CX-3271/U: (5 ft) 

Cord Assembly, Electrical: (15 ft 8 in.) SC-C-75544; 80063 

Cord, CD-307A: (6 ft) 

Filter Assembly: SM-D-536227; 80063 

Filter Assembly; SM-D-536226: 80063 

Filter: 109-D50-52; 02777 



Change 1-2.1 



TM 11-5820-256-10 


FSN. 


QUANTITY 


Nomenclature, part No., and mfr code 


AM P n/^ OCR 

AN UnU-£0U 


AN/GRO-26D 
wiin ivivvu 


581 5-51 9-6962 

JU 1 J J 1 J U JUL. 


1 


A 

1 


Frpnupnrv Shift Cnnvprtpr CV-116/IJRR CV-1 16A R C/URR 

1 1 CLJ U CI 1 L» y O 1 1 1 1 L \_/U 1 1 V CI IC 1 , w V 1 1 U/ w 1 1 1 1 j w V 1 1 U#V, 1 ' , \_// LJ 1 1 1 1 


z.qjR.-\ q?-fi774 

J J 1 J 1 J J U / / *T 


Q 
O 




fiuv M 1 ft S in ^ ^n-R-PRDfi?- RDDfi? 
"^uy. ^ i i ii j \\\. } uu u luuul, uuuuj 


5820-?22-4881 


} 




Handqpt Rnx- Sn-n-75530R- 80063 

1 1 CI 1 IUOCI UUA, \J 1 JJJUU, UUUUJ 


c;qfiE;-E;04-6?70 

JJUJ JUT U J / U 


] 




Hpadspt H-l 13/U 

1 ICCUOCL, 1 1 1 1 O/ U 


4520-224-7909 

^ J £. U L—L—^ 1 JU J 


} 




Hpptpr Rnarp Flpptrir" AAT-1S-A" 7?14? 

1 ICCllCI , OUCIUC l—ICULI IU. r\r \ 1 1 J r \ , / c_ 1 to 


4720-^20-1 995 

/ t_ U \JC-\J 1 JJJ 


} 




Hnqp Air Durt 1 996-9 1 791 32 

1 IUOC, / VI 1 UUvl. JJU J, / J 1 Jl 


5970-284-8920 






Insulator Bowl 1 S-SF 1 76626 




1 




Insulator Strain' NS4R5224 1 81349 

II 1 U 1 CI LU 1 j O LI Cll 1 1 . 1 <l Ot U J C— t.T , U 1 JT J 


^895- 922-8755 

JUJJ U t—t— U/ JJ 




A, 
1 


Intprronnprtinn Rox .l-2623/GRC- RM-D-536241 ■ 80063 

II ILCIUUI II ICUUI 1 M UUA U L—\JL—\Ji \-A 1 . \_J 1 V 1 JuULt 1 , UUUUJ 


^895-922-8746 




A 
1 


Intprronnprtinn Rox .1-2624/nRC' RM-D-5361 93 1 80063 

II ILCIUUI II ICULII 1 M UUA U <—\JL— T/ 1 . \_J 1 V 1 \—J JJU 1 JJ, UUUUJ 


5815-839-0283 




A 

1 


Interconnecting Box J-2597/GRC 


581 5-8?9-0284 

JU I J UJ J Ut.U'-r 




A 
1 


Intprronnprtinn Rny l-2 c iQ8/rnRP. 


5805-503-3395 

J U U J JUO JJJJ 


1 




Kpv KY-1 1 6/G 

i\cy i\ i i i u/ \j 


JJJJ I / I JUJU 


A 
1 




1 pad Flprtriral- H ft 6% in ^ ^M-R-1 2529?- 8006? 

LCaU , I — ICUU I Uul . \\J II U/O \\ \ . f O I VI l_J I LjLJO , UUUUJ 


t;qqt;.27q-257fi 

J \V \V J <— I U t_ \J 1 U 


A 

1 




I pad Flprtriral - M f\) WS-A4024- 05690 

LCuU , l—ICUll I L<Cl I . \ I U I \.f VVU r\TULT j U JU JU 


SQfi c i-?47-0P?1 

JJUJ J*T / \JC\J I 


A 
1 




I niidqnppkpr Aqqpmhlv I 9-Pflfi/ll - I ^-PDfiA/l I 

LUUUC3fJcar\ci nooci i iuiy , I— O cuu; «J , i_ o cuun/ »j 


5985-507-6261 

J JU J JU / ULU 1 


D 




Mast AR-155/U AR-155A R/U 

I VI CIO I , #VLJ 1 J J/ LJ , / \ 1 ' 1 JJng U/ U 


SQP0-4Q7-Rfi?4 


1 


A 

1 


Harrvinn Dpvirp MX-?87/nRA4- c ;n-n-2a057 

\-/ciiiyiiiy ucvioc ivi/\ jo / />u nnt. i— » cuuj/ 


5820-221 -1 5fi3 

JUL.U 1 1 JUO 


a 
1 


A 
1 


Onvpr 0W-124/GRA4- Sn-D-28056 

\_/U v C 1 \_/ V V 1 1 ir\t . \J\J LJ CUUJU 


5?25-497-8640 

JOCJ tj / UU^U 


4 


A 

4 


Guv Fastpnpr MX-379/IJ- Rn-D-28050 

u y i cio lci ici i vi/\ j / j/ w . ov_/ u cuuju 


5820-224-4638 

JULU tUJ J 


Q 

o 


Q 

o 


Guv Plate MX-378/L)- SC-B-28049 

VJLJy 1 ICILC IVI/\ J/ U/ LJ . n_/ LJ ^JUTJ 


c;q7t;.cin?-0702 

J J / J JUO U / Ut. 


4 


A 

4 


Guv MX-?81 A/GRA4- "^0,-0-2805? 

u y ivi/\ ju i n/unnt. o \_/ l/ luujo 


RQ7R-R?R-ni qq 

J J / J J J J U 1 J J 


4 


A 

4 


Guv MX-382A/GRA-4- Sn-D-28053 

VJUy 1 V 1 /\ OUCrVUI \f \ *"T ■ v_) v_/ U CUUJJ 


J J / J JUO U/ JO 


4 


4 


Guv mx-?8?a/gra4- c ;n-n-2ao5? 

u y ivi/\ ouorvunn't. uu I— ' CUUJO 


5985-228-8064 

JJUJ C-C-KJ UUUt^ 


I 


A 
1 


Halvard MX-51 6A/GRA-4- RO-D-28054 

1 ICliyClIU IVI/\ J 1 UrvUI l/ \ *-r. Ow l-» » tUUJT 


S1 P0-P0?-4fiSfi 

J I t.U cUJ tUJU 


A 

1 


A 
1 


Hammpr pnninpprQ Dni ihlp Fppp P 1 /P lh" rnCnCn-H-Rfi Tvnp X P.Ipqc; 1 
i idi i ii i ici , ci ly ii icci o, uuuuic i auc <— i / c iu , v_^v_j i i uu, i y fjc /\, uicioo i 


5820-240-8233 


A 

1 


A 

1 


Mast Base AB-1 54/U i SC-DL-1 82925 


JJUJ UOU t.'-rfc.U 


1 


A 

1 


Platp MflQt Rpcip" < ^P,-R-R4PQQ 

r ICllC, IVIClOl LJCLOC. OV_/ U UttJJ 


5820-227-71 fi8 

JUbU <— / / 1 uu 


Q 
O 


Q 
C) 


Mast Sprtion MR-44- RO-D-1 1 55 

IVICIOL OCULIUI 1 IVIO i i . 1 1 JJ 


4030-1 87-526? 

TUJU 1 J / JCUO 


A 

4 


A 

4 


Guv Stakp- Mptal- 18 1/4 in In- RO-DI -33399 

uuy \_Jicir\c, ivicicii, iu i / mi. ly. oo i_ jjjjj 


551 0-1 87-5267 

J J 1 U 1 J / JCU / 


A 

4 


A 

4 


Stakp Wood- 1 1/2 in dia X 30 in In ■ SO-O-22005 

ULGr\C , VVUUU, 1 \ 1 C- III. U 1 CI /\ JU III. ly . . U bCUUJ 


5985-45?-94?9 

JJUJ tJO J'-tJj 


1 


A 
1 


Trinnd Adantpr Mast AR-1 089^ VI J- Dl -"^G-R 459^57 

1 1 l|JUU AAUCipLC 1 IVICIOL rVU IUUjyy/U. UI—UU U.tJJJJ / 


5820-078-4770 

JULU U/ J i / / U 


d. 




Ma^t Ra^p MP-fiSR 

IVICIOL LJCIOU IVII \J w 1 ' 


5820-221 -5551 

JULU i—i— 1 J J J 1 


A 
1 




MflQt Rpqp MP-7R 

IVICIOL LJClOC ivin /U 


5820-1 99-8831 

JULU 1 JJ UUU 1 


"7 
1 




Mast Sprtion MS-1 16A 

IVICIOL UUIjIIUI 1 1 V 1 \~J 1 1 \J 1 \ 


JUL.U I J J OOtJ 


Q 
O 




IVICIOL UCUIIUII IVIu I I / r\ 


Rq85-1 qq-8841 

JJUJ 1 JJ JUT 1 


Q 

o 




Mast Sprtion MS-1 18A 

IVICIOL vJ UwllUI 1 1 V 1 \J 1 1 \Ji\ 


SQfiS-1 Q4-Q77D 

J JU J I J'-r <j / 1 U 


1 




Miprnnhnnp M-PQ/1 1 

1 VI 1 Ul UUI IUI 1 C IVI C-\Ji u 


5820-537-38R9 

JUCU J J / JJUJ 


A 
1 




MnHulatnr Radin Tranqmittpr MD-PWHR MD-P^QA/HR 

1 VluU LJ IdLU 1 , 1 ICIU IU 1 1 Cll IOI 1 1 1 LLCI , 1 VI LV C. J J/ u 11, 1 VI LV C. J J/\/ u 1 l 


4520-1 86-9465 

tJtU I UU \3tUJ 


1 




K/lniintinn- PR1 1 ■ 7P149 
iviuuinniy.^ui i, / 1 i to 


581 5-8^9-0299 

J J I J UO J UlJJ 




A 
1 


Mnunt MT-?298/GR- c ?n-n-?79922- 8006? 

iviuuiii ivi i jcvjo/un. uu i— ' j/ cjll, uuuuj 






A 

1 


Platform Assv "^G-D 4809?5- 8006? 

1 ICILUI 1 1 1 rAOOy . UU U.tUUJOJ, UUUUJ 


5820-538-7555 

JUl-W JJ J / J J J 


o 




Radio Rpppivpr R-390A/LJRR 

1 IdlwIIW 1 IvUvl v Ul , 1 I uJUfii Ul 11 I 


5820-237-8438 

JUCU t_ J / U*-r JU 


r\ 
d. 




Rark Flprtriral MT-655/GRG 

i iciurx, i—icuLi iucii, ivi i ujj/ui iu 


8130-174-0812 

J I JU I / i U J 1 <— 


r\ 
d. 




RppI Wirp Rl -1 59/1 J 

1 ICCI VVIIC 111— 1 JJ/ U 


JUL.U UJU fc-JUJ 


n 
<L 




RppI Rl -?q 

ncci i i l_ <j 


JU I J UO J U JUU 




A 

1 


Filtpr-Pnlar Rplav F-1084/GRG- ^M-D-5?62?2- 8006? 

i 1 1 ici i uicii nci ciy i i uut/ u nu . uivi lv joucoc , uuuuj 


581 5-503-27R0 

JU 1 J JU J <— 1 UU 


A 
1 




Rpnprfnratnr Tran^mittpr TT-7fi/0.0.C 

IlCUCIIUICILUI, IICIIIOIIIILLCI, 1 1 / U/ UU U 


541 0-1 ?2-6679 

Jt 1 U 1 Jt. UU / J 


A 
1 




Chpltpr Flpptripal Fnuinmpnt R-Sfi/H R-SfiA/H 

UNCI LC 1 , 1 — ICUU IUCII l_U|UIUIIICIIL U JU/ U , U JUH/ u 


5940-577-7076 

J J iu J / / / U / U 


\ d. 




Snlirp Condurtor- KS-90- 09922 

UkVllUC UUI IUUUIUI . 1 \U JU, W \V vV t_ t_ 


6625-682-4464 


A 

1 




Standina Wave Ratio Power Meter ME-1 65/G 


5930-548-6806 

JJJU JtU uuuu 


A 
1 




Switrh Rox SA-331/U 

U Vvl IUI 1 UUA U#V J J 1 / U 


5820-947-3253 

JUCU JT / OCJO 


1 




Switrh Flprtrir SA-1 235/GRG-26D- SG-D480956- 80063 

UVvlLUI 1, 1 ICULI IU U#V 1 kJJ/U 1 IU L.UIV , UU U^UUJJU, UUUUJ 


5805-541-001 2 

JUU J JtJ UU I i— 


2 




Tplpnhnnp ^pt TA-91 P/PT 

1 ClCUl IUI IC UCl 1 f \ J 1 C-i \ 1 


5815-557-5970 


2 




Teletypewriter Set AN/UGC4 


5815-392-7743 


2 




Teletypewriter Set AN/FGC-20X 


5820-503-2640 


1 




Transmitter, Radio T-368/URT, T-368A, B, C, D, E/URT 


5820-681-9824 


1 




Tuner, Radio, TN-339/GR 


6145-160-5058 


500 ft 




Wire, Electrical W-146 




5 




Paper, Teletype: UU-P547E; 82865 








Change 2 1-2.2 



TM 11-5820-256-10 



FSN 


QUANTITY 


Nnmpnrlaturp nart Nn and mfr mdp 


AN GRC-26D 


AN/GRC-26D 
with MWO 


5815-503-2621 


2 




Table, Teletypewriter FN-59/FG 


5815-503-1530 


1 




Table, Teletypewriter, FN-64/MGC 


7530-634-6237 


15 




Tape, Recording: UUT-T-1 20:82869 



NOTE 

For requisitioning purposes, the Federal stock number must be converted to the 
National stock number by adding "-00-" after the Federal stock classification (FSC) 
code (first four digits). For example, FSN 58155196962 converts to NSN 581500-519- 
6962. 



Change 2 1-2.3 



1-5.2. Expendable Consumable Items 

A list of expendable consumab le items required for 
operation appears in I table 1-11 and are required for 
operation of this equipment. They are authorized to be 
requisitioned by SB 700-50. The FSN for the applicable 
unit of issue required can be found in appropriate supply 
catalogs. The FSCM is used as an element in item 
identification to designate manufacturer, distributor, or 
Government agency, etc, and is identified in SB 70842. 



TM 11-5820-256-10 

Table 1-1. Expendable Consumable 

Supplies and Material 

fief Afo. 



Item 


Description 


and FSCM 


FSC 


1 


Adhesive 


4-752; 22428 


8150 


2 


Clip, Paper 




4290 


3 


Clip, Paper 




4290 


4 


Cord, Cotton 




3404 


5 


Oil, Lubricating 


644A; 96906 




6 


Paper, Teletype 


00-P547E 
82865 




7 


Pencil 




8697 


8 


Tape, Recording 


UU-T-120; 
82869 


6237 



Change 1 1-2.4 



1-5.2. Expendable Consumable Items 

A list of expendable consumab le items required for 
operation appears in I table 1-11 and are required for 
operation of this equipment. 

The FSN for the applicable unit of issue required can be 
found in appropriate supply catalogs. The FSCM is used 
as an element in item identification to designate 
manufacturer, distributor, or Government agency, etc, 
and is identified in SB 70842. 



TM 11-5820-256-10 

Table 1-1. Expendable Consumable 

Supplies and Material 

fief Afo. 



Item 


Description 


and FSCM 


FSC 


1 


Adhesive 


4-752; 22428 


8150 


2 


Clip, Paper 




4290 


3 


Clip, Paper 




4290 


4 


Cord, Cotton 




3404 


5 


Oil, Lubricating 


644A; 96906 




6 


Paper, Teletype 


00-P547E 
82865 




7 


Pencil 




8697 


8 


Tape, Recording 


UU-T-120; 
82869 


6237 



Change 4 1-2.5 



TM 11-5820-256-10 



1-6. Nomenclature and Common Names 

A list of the nomenclature assignments for those 
components of Radio Set AN/GRC-26D that are 
assigned common names is given below. The power 
units listed are not part of Radio Set AN/ GRC-26D but 
may be used with it. 



Nomenclature 



Common name 



Cabinet, Electrical Equip- 
ment CY-1807/G. 
Cabinet, Storage CY- 

1721 (*)/GRC. 
Control, Radio Set C 

1123/GRC. 
Control, Remote switching 

C1474/GRC. 
Converter, Frequency Shift 

CV-116(*)/URR. 
Generator Set, Gasoline 

Engine, Trailer Mounted 

PU-619/M 



Equipment cabinet 
Storage cabinet 



Control unit 



Remote control unit 



Converter 



Power unit 



Headset 



Headset, Electrical H- 
113/U. 

Key, Telegraph KY-1 1 6/U 
loudspeaker Assembly 

LS-206(*)/U. 
Microphone M-29(*)/U 
Modulator, Radio MD- 

239(*)/GR. 
Radio Set AN/GRC-26D 
Receiver, Radio R-390 Receiver 

(*)/URR. 
Reperforator-Transmitter, 

Teletypewriter TT-76 

(*)/GGC. 
Shelter, Electrical Equip- 
ment S-56(*)/G. 
Standing Wave Ratio-Power Matching unit 

Meter ME-165/G. 
Teletypewriter TT-98(*)/ 

FG. 

Transmitter, Radio T- 

368(*)/URT. 
Tuner, Radio Frequency 

TN-339/GR. 



Key 

Speaker assembly 

Microphone 
Fsk-modulator 

Radio set 



Reperforator 



Shelter 



Page printer 



Transmitter 



Tuning unit 



1-7. Radio Set AN/GRC-26D 

a. The radio set contains two receivers, a 
transmitter, an fsk-modulator, a converter, a tuning, unit, 
a control unit, a reperforator, a remote control unit, a 
power unit, the shelter, two page printers, three whip 
antennas, and three doublet antennas, interconnecting 
cables, and accessory components a nd spare parts. A 
complete listing of components is in l paragraph 1-5.1 1 



I Figures 1-4| through |1-10| show interior views of the 
shelter. 

b. All components of the radio set except the 
antennas, the remote control unit, and the power unit are 
housed within the shelter during operation. 

c. The radio set can be o perated f rom a re mote 
site with the remote control units ( If ig . 1-1 1 l and l 1 -1 21 . 

d. The radio set receives its operating power from 
the trailer mounted power unit. 

1-8. Shelter, Electrical Equipment S-56(*)/G 



a. The shelter ITfTg. 1-2| and 1 1-3)1 is an insulated 
steel and plywood structure that houses the components 
of the radio set. Six wall windows and the window in the 
rear door have screens and shutters. A roof hatch is 
provided in Shelter, Electrical Equipment S-56A/G only. 
The windows and hatch may be opened for ventilation. 
Interior wiring, electrical outlets, fluorescent lights, a 
window fan, and a ventilating blower are permanent parts 
of the 'shelter. Housekeeping and firefighting equipments 
are mounted in the shelter. 

b. The power for the operation of the radio set is 
connected to the shelter circuit breakers through the 
power input feedthrough receptacle mounted in the rear 
wall of the shelter. The circuit breaker housing contains 
eight circuit breakers Iffig. 1-91 . Two are high current 
circuit breakers for the main alternating current (ac) line; 
four are low current circuit breakers; one is for the 
transmitter; one is for , lights; one is for the heater and 
fans; one is for the remainder of the equipment; two are 
not connected. 

c. The shelter is mounted on a standard 80- by 
144-inch cargo truck b ody for t ransportation or mobile 
operation. Lifting straps [fig. 1-3)1 are used when hoisting 
the shelter onto the truck. Two holddown assemblies on 
each side of the shelter secure it to the cargo truck body. 
Four anchor rings secure the shelter to the cargo truck if 
the truck bed is a wooden platform. 

d. The connections between the doublet antennas 
and the receivers are made throug h the re ceiving 
doublet antenna feedthrough receptacle l (fig. 1-21 ) on the 
front wall of the shelter. The connections to the remote 
line are made through the remote control unit 
feedthrough receptacle in the curbside wall of the 
shelter. Connections to the whip antennas are made 
through feedthrough receptacles in each whip mount 



Change 4 1-3 



TM 11-5820-256-10 



ing bracket. Two Mast Brackets MP-50-(*), which 
support the receiving antennas, are secured to the front 
wall of the shelter. Bracket MT657/GRC, which supports 
the transmitting antenna, is secured to the rear wall of 
the shelter. 

1-9. Blower Assembly, Electrical HD-223/G 

Blower Assembly, Electrical HD-223/G, mounted in the 
equipment cabinet, provides air circulation for the 
equipment mounted in the equipment cabinet. 

1-10. C ontrol, Radio Set C-1 123/GRC 

Iffia~3^2l[3^3l1 

a. The control unfit ! (fig. is the control center for 
the radio set. The control unit routes the signals to be 
transmitted or received to the proper components of the 
radio set for each particular type of operation (fsk, am. 
voice, cw, fsk am., and cryptographic (crypto). The 
control unit receives mark and space signals from- the 



converter and directs them to the teletypewriter 
equipment through Junction Boxes J-2597/GRC and J- 
2598/GRC. The control unit receives signals originating 
from the teletypewriter equipment, and directs them from 
Junction Boxes J2597/GRC and J-2598/GRC to the fsk- 
modulator; signals initiated by the microphone, 
telephone, or key are directed to the transmitter. During 
operation with crypto equipment, the signals are routed 
through the crypto equipment instead of Junction Boxes 
J-2597/GRC and J2598/GRC. 

b. The control unit is housed in a smooth, gray- 
enameled metal case and mounted on the curbside wall 
above the teletypewriter equipment. The operating 
controls are on the front panel. The top and two sides of 
the control unit contain jacks and binding posts for 
connections to the other equipments of the radio set. 

1-11. Convert er, Frequency Shift CV-1 16(*)/ URR 

The converter, mounted in the equipment cabinet, 
converts frequency-shifted signals into direct current (dc) 



MAST BRACKET 

MP-50-W WAST BRACKET 




Figure 1-2. Shelter, Electrical Equipment S-56(*)/G, front oblique view. 

Change 4 1-4 




Figure 1-3. Shelter, Electrical Equipment S-56(*)/G, rear oblique view. 



pulses. Refer to TM 1 1-2241 for a detailed description. 

1-12. R eceiver, Radio R-390(*)/URR 

ET4) 

Two receivers, mounted in the equipment cabinet, 
provide for reception of cw, am. voice, fsk, and fsk-am. 
signals within a frequency range of 0.5 to 32.0 MHz. For 
a detailed description of the R-390/URR, refer to TM 1 1- 
5820-357-10. For a detailed description of the R- 
390A/URR, refer to TAI 1 1 -5820-358-1 0. 

1-13. Reperforator-Transmitter, Teletypewriter 
TT-76Q /GGC 

|gia^4l and rr9)1 

The reperforator, mounted on Teletypewriter Table FN- 
64/MGC, transmits and receives teletypewriter 
messages. Refer to TM 11-5815-238-12 for a detailed 
description. 

1-14. T eletypew riter TT-98(*)/FG 

Two page printers, mounted on Teletypewriter Tables 
FN-59/FG adjacent to the curbside wall, 



transmit and receive teletypewriter messages. Refer to 
TM 1 1 -581 5-200-1 2 for a detailed description. 

1-15. L oudspea ker Assembly LS-206Q/U 

The speaker assembly, mounted in the equipment 
cabinet, provides a means by which the audio signals 
may be monitored. The speaker assembly houses two 6- 
inch speakers, the transformers, and the selector 
switches, which are mounted on the front panel. 

1-16. Modulato r, Radio MD-239(*)/GR 

ffiaT9) 

The fsk-modulator provides the required frequency shift 
for radio transmission of teletypewriter signals. The fsk- 
modulator is bolted to the top of the transmitter. It is 
contained in a smooth, gray- enameled metal cabinet. 
Operating controls are on the front panel. A power input 
jack, a blower jack, and a teletypewriter input jack are 
mounted on the rear of the chassis. A blower is mounted 
on the rear of the cabinet; ventilation screens are near 
the front of the cabinet. 



1-5 



TM 11-5820-256-10 



1-17. Transmitter, Radio T368n/URT l(fia. 1-9) 

The transmitter is used for the transmission of cw, am. 
voice, fsk, and fsk-am. signals within a frequency range 
of 1.5 to 20 MHz. Refer to TM 11-809-10 for a detailed 
description. 

1-18. Standing Wave Ratio-Power Meter ME-1 65/G 
ffia. 1-9) 

The matching unit, mounted on the curbside wall, 
provides a noninductive dummy load of 52 ohms. It 
permits direct readings of the transmitter power output 
and the standing wave ratio (swr) between the 
transmitter and its load. Refer to TM 11-6625-233-15 for 
a description. 

1-19. Tuner, Radio Frequency TN339/GR |(fiq. 1-9) 

The tuning unit, mounted on the top of the transmitter, 
provides a means of adjusting the electrical length of the 
transmitting whip antenna. Refer to TAI 11-809-10 for a 
detailed description. 

1-20. Telephone Set TA-312/PT 

Telephone Set TA-3'12/PT is mounted in the handset 
box, which is secured to the forward side of the storage 
cabinet. The TA-312/PT provides telephone facilities 
between radio sets. On early orders of the radio set, 
Telephone Set TA-43/ PT was used. For a detailed 
description of the TA-312/PT, refer to TM 1 1 -5805-201 - 
12. For a detailed description of the TA-43/PT, refer to 
TAI 11-337. 

1-21. Control, R em ote Sw itching C-1474/GRC 
tfia. 1-TTl and FM2T1 

The remote control unit controls the operation of the 
radio set from a remote site. The remote control unit 
consists of binding posts and jacks in a metal housing. 
On the right panel are four sets of binding posts: ONE 
WAY, REMOTE TEL., REC. DX, and LOCAL TEL. The 
XMITR ON switch is on the front panel, and six 
telephone jacks are on the left panel. The TTY SWITCH 
coaxial connector is below the telephone jacks. A 
bracket at the top of the unit is for mounting t he remote 
control unit. The modified remote control unit ffia. 1-12} 
has three jacks and two connectors on the right panel. 
The jacks are labeled LOC TEL, REC DX, and ONE 
WAY OR SEND DX. The connectors are labeled 
REMOTE and TTY SWITCH. The XMITR ON 



switch is on the front panel. A bracket at the top of the 
unit is for mounting the unlit. 

1-22. Interconnecting Box J-2623/GRC [fig. 1-13| and 

During remote operation, Interconnecting Box 
J2623/GRC provides termination points from Control, 
Radio Set C-1123/GRC, located in the shelter, to 
Interconnecting Box J-2624/GRC at V the remote site. 
Three cables from the shelter are connected to 
connectors J1, J2, and J3 of the J-2624/GRC at the 
remote site. The back plate of the J-2623/GRC is 
designed in the form of a hook for mounting outside the 
shelter. 

1-23. interconnecting Box J-2624/GRC l(fiq. 1-15) 

Interconnecting Box J-2624/GRC is used during remote 
operation to accept field wire connections to its binding 
posts El through E7 from binding posts El through E7 of 
Interconnecting Box J2623/GRC and to provide 
termination for a cable from the J-2623/GRC to Control, 
Remote Switching C-]474/GRC at the remote site. 

1-24. Junction Box J-2597/GRC I(fiq. 1-8l 

Junction Box J-2597/GRC has five connectors and five 
binding posts. The connectors are designated J3 LOOP 
IN 1 , J7 LOOP OUT 1 , J4 LOOP IN 1 , J8 LOOP OUT 2, 
J9 TRANS VOICE GRD. The binding posts are 
designated El, E2, E3, E4, and E5. The J-2597/GRC is 
used between the teletypewriter equipment and Control, 
Radio Set C-1123/GRC to provide through connections 
when security equipment is not being used. Four captive 
screws fasten this unit to the center shelf of the 
equipment rack. 

1-25. Junction Box J-2598/GRC lma. 1-8l 

Junction Box J-2598/GRC has two connectors and three 
binding posts. The connectors are designated J7 LOOP 
OUT 1 and J8 LOOP OUT 2. 
The binding posts are designated El, E2, and E3. 
The J-2598/GRC is used between the teletypewriter 
equipment and Control, Radio Set C-1123/ GRC to 
provide through connections when security equipment is 
not being used. Four captive screws fasten this unit to 
the equipment rack. 

1-26. Deleted. 



Change 4 1-6 



1-27. Generator Set, Gasoline Engine, Trailer 
Mounted 

Power requirements for the AN/GR-26D are usually 
satisfied by the use of two 10 kw, gasoline powered, 
motor generator sets, with accessories, mounted on a 1- 
1 /2-ton trailer. The PU-619M (TM 56115275-15 and TM 
52805259-14) or equivalent may be used. 

1-28. Operating Accessories 

a. Headset, Electrical H-113/U (4, Ifiq. B-12)| . The 
headset consists of two earphones mounted on an 
adjustable headband and a connecting cord and plug 
that extends 18 inches from the right earphone. The 
earphones are provided with rubber cushions. On an 
early order of the radio, set, Headset, Electrical (Navy 
type 49507) was supplied, which may be used 
interchangeably with the H-1 1 3/U. 

b. Microphone M-29(*)/U (7, Ifiq. B-4).l The 
microphone is a unidirectional, low-impedance, carbon 
button, handheld microphone. It is provided with a cord 
terminated in an adapter plug at one end and in the 
microphone through a switch at the other end. A metal 
hanger is at the top of the handle. The microphone is 
connected to the MIC OR KEY jack on the control unit 
and operated by the press-to-talk swit ch on the handle. 

c. Key, Telegraph KY-116/U (4. I fia. B-41 . The key 
is attached to a metal clamp that can be mounted on the 
operator's leg. The key is equipped with four brass 
screws for mechanical adjustments and two brass 
screws for connecting the key to Cable Assembly, 
Special Purpose, Electrical CX-1852/U. On an early 
order of the radio set, Key J-45 was supplied. The J-45 
is connected to Cord CD-201 which has a plug at the 
free end. 

d. Whip Antennas. One transmitting and two 
receiving whip antennas are furnished. 

(1) Each receiving whip antenna consists of 
two Mast Sections MS-1 16A, one Mast Section MS-1 17- 
A, and one Mast Section MS-118-A, which are 
assembled and inserted in Mast Base MP-65B. Mast 
Base MP65-B is mounted on Mast Bracket MP-50-(*), 
which is secured to the front exterior wall of the shelter 
ffig. 1-21 The whips are tied down with insulated guy 
assemblies when the radio set is operated while in 
motion. 



(2) The transmitting whip antenna consists of 
three Mast Sections MS-116-A, one Mast Section 
MS117-A, and one Mast Section MS-118-A, which are 
assembled and inserted in Mast Base MP-76. Mast Base 
MP-76 is mounted on Bracket MT-657/GRC and secured 
to the outside rear wall of the shelter. An insulated guy 
assembly is provided to tie the transmitting whip antenna 
in a horizontal position when the radio set is operated 

while in motion. 

e. Doublet Antennas. Six Masts AB-115(*)/U Rfigl 

ITT71) and 1 ,000 feet of Wire W-1 are furnished for the 
construction of half-wave doublet antennas. At 
frequencies from 1 .5 to 4.0 MHz, three Masts 
AB115(*)/U are used to support each doublet antenna; 
therefore, two antennas may be erected: one for 
receiving, and one for transmitting. At frequencies from 
4.0 to 20.0 MHz, where shorter wire lengths are required, 
two Masts AB-115(*)/U are used to support each 
doublet; therefore, three antennas may be erected: two 
for receiving, and one for transmitting. Two Cable 
Assemblies, Radio Frequency CG-1334/U, each 500 feet 
long, are used for receiving antenna lead-ins. One RF 
Cable Assembly CG-692/U, 75 feet long, i s used as a 
transmission line for the transmitting doublet. [Figure 1-171 
shows the components of one complete Mast AB- 

155(*)/U. 

f. S witch Box SA-331/U. The SA-331/U Kfia. 1-181 
land 1-19] , used with the motor-generators and mounted 
on the motor-generator trailer. It enables the operator to 
switch from one motor-generator to the other without 
interrupting the operation of the radio set. The SA-331/U 
is almost cubical. It is secured in its case by six captive 
screws on the front and eight captive screws at the rear. 
The input and output connectors are at the rear of the 
SA-331/U. 

1-29. Nonoperating Components 

a. Cabinet, Electrical Equipment CY-1807/G Kfiq.l 
1 1-4|) . The metal equipment cabinet is a rack-type cabinet 
that houses the two receivers, a converter, a speaker 
assembly, and Blower Assembly, Electrical HD-223/G. 
The equipment cabinet is shock mounted to the floor and 
wall of the shelter. A stainless-steel utility table can be 
fastened to the front of the equipment cabinet at the 
correct servicing height for the three major components 
in the equipment cabinet. When not in use, the utility 
table is attached to the shelter wall by brackets. 



Change 4 1-7 




1-8 



TM 11-5820-256-10 



CONVERTER CAB] MET. 

FREQUENCY ELECTRICAL 

SHIFT EQUIPMENT 

CV - II 6( *), URH CY —I &07/G 



A RECEIVER, RADIO B RECEIVER. RADIO 
R -39ft(tj URH R -330C1 URR 



HEATER . 



FIRE 

EXTINGUISHER 



CABINET STORAGE 

CY -I72l(*). GRC 

LGUDSPEAKEH 
ASSEMBLY 
LS ~106(*3 U 



SECURITY FILE 
ISAFfi) 




TELETYPE WRITER 
TT-9Bl*J FG 

TELETYPEWRITER 

TABLE 

FN -55 FG 



TRANSMITTER, 
RADIO 

T -368i': URT 



BLOWER, ASSEMBLY 
ELECTRICAL HD -2!3 



HACK MOUNTING 



TM5SZO-2S«~IO 10 © 



Figure 1-5. Radio Set A N/GRC-26D, interior view from rear door (modified 
per MWO 1 1 -5820-256-35/1). 



b. Cabinet, Storage CY-1721 (*)/GRC I /fig. 1-4l 
The storage cabinet is adjacent to the roadside wall of 
the shelter and is secured to the shelter floor and wall by 
rotolock fasteners. The metallic cabinet has an exterior 
finish of smooth, gray enamel. The tabletop of the 
storage cabinet is of Formica material. Sliding drawers 
with rollers provide storage for minor components and 
accessories of the radio set. 



c. Clock [fig. 1-4)1 . The clock is mounted in a metal 
case. The mounting frame has four holes which are for 
mounting of the dock on the curt>side wall above the 
teletypewriter e quipment . 

d. Heater fflg. 1-4| The heater is housed in a black 
metal case with a cast aluminum grid. It operates on 
115-volt, 50- to 60-Hertz (Hz), single-phase ac and 
consumes 1 ,500 watts. A thermal reset switch is on the 
front panel below the grid. 



1-9 



TM 11-5820-256-10 




1-10 



TM 11-5820-256-10 



FIRE 

EXTINGUISHER 




CABINET STORAGE 
CY— |?2l[«) GRC 



SECURITY FILfc 
i SAFE ! 




HEATER 



TM5820-i56-l0-l0(5 



Figure 1-7. Radio Set AN/GRC-26D, interior roadside view from rear door 
(modified per MWO 11 -5820-256-$5/1 ) 



A fan, mounted in front of the heater element, circulates 
the heated air. A toggle switch on the top panel of the 
housing allows the fan to be operated independent of 
heat, but heat cannot be turned on without placing the 
fan in operation. Four wing-type Dzus fasteners secure 
the heater to the heater mounting plate which is secured 

to the floor of the shelter. 

e. Rack, Mounting MT-3298/GRC [fig. 1-8)1 Rack, 
Mounting MT-3298/G RC is a metal rack designed for 
holding Power Supply PP-978/FG when it is mounted in 
the equipment rack. Jacks marked AC IN and DC OUT 
are provided on the -rack. 



1-30. Differences in Models 

All Radio Sets AN/GRC-26D are similar in purpose and 
operation. The differences the operator is concerned with 
are the modem designations of the major components 
and application of MWO 11-5820-256-35/1. This 
modification provides Radio Set AN/GRC-26D with a 
capability for crypto operation. Operating procedures with 
crypto facility installed are the same as normal 
operating procedures, except that Switch, Electronic SA- 
1253/GRC must be operated to the correct position. 
Although the use of different 



1-11 




POWER SUPPLY 

PP — 978, FG 



RACK, MOUNTING 
MT- 3298 GRC 




Figure 1-8. Rack mounting equipment 



models of the same components may result in minor 
changes in the operating procedure, these differences 
are covered in the technical manuals for the individual 
components (app A). 



Other differences between models of the radio set which 
do not change the operating procedures are listed in the 
chart below. 



1-12 



TM 11-5820-256-10 




Figure 1-9. Radio Set AN/GRC-26D, interior view. 
1-13 



TM 11-5820-256-10 



STANDING WAVE POLAR RELAY MODULATOR 

RATIO-POWER METER ASSEMBLY RAPtO CIRCUIT 

is F -I084 GRC MD-239f* GR BLOWER BREAKERS 




REPERFORATOR TELETYPEWRITER 

TRANSMITTER TABLE 

TELETY PE WHITER FN-«d, MGC 
TT-76(*)/GGC 




Figure 1-10. Radio Set AN/GRC-26D, interior rear view (modified per MWO 

11-5820-256-35-/1). 



1-14 



TM 11-5820-256-10 



Order No. 25209-Phili-M4 Order No. 28459-Phila-55 and Order No. 43066-Phil-56 and 3219-PP-59 

21316-Phila-56 



Headset, Electrical (Navy type 49507) ....Headset, Electrical H-113/U Headset, Electrical H-1I13/U. 

Reel DR-4 Reel RL-159 Reel RI-159. 

Key J45 Key, Telegraph KY-1 1 6/U Key, Telegraph KY-1 1 6/U. 

Telephone Set TA-43/PT Telephone Set TA-43/PT Telephone Set TA-312/PT. 




Figure 1-11. Control, Remote Switching C-1474/GRC, oblique view. 



1-15 



TM 11-5820-256-10 




TM 5820-256-10-33(1) 

Figure 1-12. Control, Remote Switching C-1474/GRC, leftside view 
(modified per MWO 1 1 -5820-2564-5/1 ). 

1-16 



TM 11-5820-256-10 




1-17 



TM 11-5820-256-10 




TM 5620-256 \Q- 47 

Figure 1-15. Interconnecting Box J-2624/GRC. 



1-18 




Figure 1-16. Generator set, gasoline engine, trailer mounted 
(typical), with accessory components. 



Change 4 1-19 



TM 11-5820-256-10 



cswif • -no device 



COVE" 
CW-l£4/u»4-« 



6 Guv S"ia«£S 



6 GUT fiSTEMEBS 
MX - 3 / U 



a MAST SECTIONS 



CJ1RBYIBS DEVICE 




5 GUY PL1TES 

«s-ve/u 



u(st sase 
PL ATE 



. UY 

tlj.JBHH/Sfli-* 
( * SuPPLlE D i 



GUT 

.4 5 J PP LI £ ! 



HICKORY STAKES 
14 SUPPLCED) 



HA1 TftHO 



Figure 1-17. Mast AB-155(*)/U, components. 
Change 4 1-20 



TM 11-5820-256-10 




1-21 




Figure 1-19. Switch Box SA-331/U, rear view. 



1-22 



TM 11-5820-256-10 



CHAPTER 2 
INSTALLATION 

WARNING 

During installation of this equipment, conform to all safety requirements in TB SIG 291. Injury or death 
could result from failure to comply with safe practices. 



2-1. Siting 

When selecting the antenna site, consider the following: 

a. Radio signals are absorbed and sometimes 
reflected by nearby obstructions, such as hills, metal 
buildings, and bridges, or by tele phone line s that extend 
above the height of the antenna \f\g. 1-1)1 Transmitted 



signals have a greater range when the antenna is as 
high above ground as possible. Transmission and 
reception are best over water or level ground. 

b. If transmission and reception in all directions are 
required, place the antenna on the highest hill within the 
designated area. 

c. When in rear areas, avoid placing the radio set 
near sources of electrical interference, such as power or 
telephone lines and radar equipment. 

d. Try several locations within the general area, 
and select the one that provides the best signals from 
the desired stations. 

e. Enemy jamming action against the receiver is 
always a possibility. The effects of enemy jamming may 
be reduced by locating the antenna so that nearby 
obstructions act as a screen in the direction of probable 
sites 9f enemy jamming transmitters. This screening 
action may also reduce the transmitted signal strength in 
a direction toward the enemy and thereby make it more 
difficult for the enemy to intercept the signals. 

f. For space diversity reception, a clear area 
suitable for the erection of two doublet receiving 
antennas is required. The receiving antennas should be 
separated by at least three wavelengths or more at the 
operating frequency, but the separation should not 
exceed 900 feet. The best reception is possible when 
the receiving antennas are perpendicular or broadside to 
the desired incoming signal and in line with transmitted 
signals from local installations. For each receiving 
antenna, a clear level area, the size of which is 
determined by the frequency of operation, is desirable. 
At 2 MHz, each antenna will require an area of 285 feet 
by 50 feet, with the long dimension perpendicular to the 
direction or reception. At 18 MHz, each antenna will 
require an area of 180 feet by 50 feet. The shelter 
should be midway between the two receiving antennas. 



For a long-wire transmitting antenna, a level area of 
approximately 200 feet by 40 feet by 40 feet is required. 
The center of the transmitting antenna should be 
approximately 30 feet from the shelter. 

g. Where a large number of radio sets are in 
operation, careful layout of the numerous antennas is 
necessary. Improper layouts will cause mutual 
interference between the various radio sets. This 
interference may be great enough to affect the 
intelligibility of the incoming signals. Mutual interference 
from nearby transmitters may be reduced by separating 
the receiving antennas from the interfering transmitting 
antennas as much as possible. Other means of 
reducing interference are orienting the antennas to take 
best advantage of their directional patterns, selecting 
operating frequencies properly, tuning transmitters 
accurately, and aligning receivers properly. 

2-2. Unpacking 

When packed for shipment, the major components, 
accessories, and spare parts for the radio set are 
mounted or stored in designated cabinets, 
compartments, shelf space, or chests within the shelter. 
The overflow components, accessories, and spare parts 
are placed within 'a wooden box. The wooden box is 39 
inches long, 23 inches wide, 23 inches deep, and has a 
volume of 14.5 cubic feet. Cables properly coiled, 
antenna equipment chests, and the overflow box are 
stored on the shelter floor. Cabinets and chests are 
secured with fastening devices. Components on shelves 
are blocked, braced, tied, or strapped to protect the 
items against movement and transportation hazards. All 
shelter windows, blackout blinds, doors, and louvers are 
closed and secured. Antenna openings and all other 
openings are covered with caps provided or with properly 
secured sheet metal plates or wooden plugs. 

a. General. Be careful in unpacking. Do not thrust 
tools into the interior of any container or wrap. 

b. Unpacking. Remove the caps, covers, plates, 
and plugs from the openings. Open the shelter doors 
and dismantle the wooden blocking and bracing frames. 



2-1 



TM 11-5820-256-10 



Remove and open the overflow boxes. Remove all other 
ties and blocking material used to secure the 
components in the shelter. 

2-3. Checking Unpacked Equipment 

a. Inspect the equipment for damage that may 
have been incurred during shipment. If the equip ment 
has been damaged, fill out and forward DD Form 6 tparal 

Q3b). 

b. Check to see that the equipment is complete as 
listed on the packing slip. 

c. If the equipment has been reconditioned, see if it 
has changed by a modification work order (MWO). If 
modified, the MWO number will appear on the front near 
the nomenclature plate. Check to see that all the 
MWO's have been completed. Additional MWO's may 
need to be performed. 

2-4. Installation of Shelter, Electrical Equipment S- 

56(*)/G 

If the radio set is to be used as a mobile station, the 
shelt er should be installed on a 2 1/2 -ton, 6 by 6 cargo 
truck |(fiq. 1-1] . Use the following procedures for setting 
up the radio set for mobile use. 

a. Remove the canvas cover and side framing from 
the truck. Drop the tailgate. 

b. Obtain a hoist capable of lifting the shelter. Lift 
the shelter by its four lifting straps, and place it on the 
truck body with the entrance door toward the rear of the 
truck. If a hoist is not available, skids may be used to 
slide the shelter onto the truck. Skid Equipment MX- 
1 57/U may be used for this purpose. 

c. Attach the holddown clamps on the shelter to the 
truck body sides to hold the shelter firmly in place. If the 
cargo truck has a wood en platfor m, secure the shelter 
with the four anchor rings Iff ig . 1-31 . 

d. Couple the power unit trailer to the rear of the 
truck. 

2-5. Installation of Whip Antennas 

WARNING 

Safety precautions must be observed 
when installing the whip antennas on the 
outside of the shelter. Death can occur 
if an antenna comes in contact with 
electrical power lines. Prior to 
installation of the whip antennas, survey 
the area carefully for location of power 
lines, their height above ground level, 
and their proximity to the installation site. 
The antenna must be installed as far 



away as possible from electrical power 
lines, and never closer than twice the 
height of the antenna. 

a. Check to see that the antenna bracket 
assem blies and m ast base s have been installed on the 
shelter If fig . 1-2| and l 1-3)1 Install the transmitting and 
receiving whip antennas as instructed in b through d 
below. 

b. Select the following items from the storage 
cabinet: 



Quantity 



Item 



7 Mast Section MS-116-A 

3 Mast Section MS-118-A 

3 Mast Section MS-I18-A 

2 Receiving whip antenna insulated guy assembly 

1 Transmitting whip antenna insulated guy assembly 

c. Assemble a receiving antenna as follows: 

(1) Screw one Mast Section MS-116-A into 
another MS-1 1 6-A. Be sure that the connection is tight. 

(2) Screw one Mast Section MS-117-A into 
one Mast Section MS-118-A. Be sure that the 
connection is tight. 

(3) Screw the MS-1 1 6-A into the MS-117-A. 
One receiving antenna will consist of two MS-116-A's, 
one MS-1 1 7-A, and one MS-1 1 8-A. 

(4) Screw the MS-1 1 6-A into Mast Base MP- 
65-B mounted on the exterior front wall. 

(5) Assemble another receiving antenna as 
described in (1) through (3) above. Screw the completed 
antenna into the other Mast Base MP-65-B on the 
exterior front wall. 

(6) If the radio set is to be operated while in 
motion, attach the whip antenna holddown guys for the 
receiving antennas at the junction of the third and fourth 
mast sections. Pull the antenna down to a forward 
horizontal position. Secure the other ends of the whip 
antenna holddown guys to the headlight grille or front 
bumper of the truck. 

d. Assemble the transmitting antenna as follows: 

(1) Screw three Mast Sections MS-1 1 6-A 
together, and tighten the connections. 

(2) Screw one Mast Section MS-1 1 7-A into a 
Mast Section MS-1 1 8-A, and tighten the connection. 

(3) Screw the two assembled mast sections 
together. One transmitting antenna will consist of three 
MS-1 1 6-A's and one each MS-1 1 7-A and MS-1 1 8-A. 

(4) Screw the assembled mast sections into 
Mast Base MP-76. 



Change 4 2-2 



TM 11-5820-256-10 



(5) If the radio set is to be operated while in motion, 
'bend the antenna backward to a horizontal position and 
attach the whip antenna holddown guy rope to the top of 
the highest MS-1 1 6-A. Attach the other end of the guy to 
the power unit trailer. 

2-6. Installation of Doublet Antennas and Mast AB- 
155(*)/U 

a. General. The doublet antenna equipment 
furnished with Radio Set AN/GRC-26D may be used 
instead of the whip antennas when operating from a 
fixed or semifixed location to provide greater directivity or 
signal pickup. When the AN/GRC-26D is operated within 
the frequency range of 1 .5 to 4.0 MHz, the length of the 
antenna wire requires the use of three 40-foot Masts AB- 
155(*)/U for each antenna. At frequencies above 4.0 
MHz, only two masts are required for each antenna. 
Each antenna should be positioned broadside to the 
direction of transmission or reception. When space 
diversity reception is used, the receiving antenna's 
should be separated by at least three wavelengths at the 
lowest frequency. 

b. Antenna Construction. The antenna is a half- 
wave doublet which is normally operated at the half-wave 
fundamental of the desired frequency. If the antenna is 
to operate on more than one frequency, the radiating 
portion may be of a number of predetermined lengths of 
Wire W-1 separated by strain insulators and 
interconnected as required by jumpers. Construct the 
antenna as follows: 

(1) List the operating freq uencies. 

(2) Refer t d figure 2-2] and determine the 
overall antenna length for the fundamental frequency of 
each frequency assigned. 

(3) Divide each overall antenna length ((2) 
above) by 2. This gives the antenna length, including 
strain insulators, of each side measuring from the coaxial 
connector. 

(4) Attach one end o f the antenna wire to the 
coaxial connector (B, |fig. 2T] ; use a splice conductor 
and the wingnut on the coaxial connector. Run out the 
required length of Wire W-1 for the highest fundamental 
frequency to be used ((3) above), and connect it to the 
strain insulator. Construct the other half of the antenna 
in exactly the same manner. 

(5) Attach the antenna wire for the next lower 
frequency to the unused end of the strain insulator of the 
antenna already constructed ((4) above). Allow enough 
wire for a jumper connection. Run out enough Wire W-1 
to obtain the total length required (difference "between 



highest frequency length and length required) for this 
frequency ((3) above) as measured from the center of 
the coaxial connector to the end of the section being 
constructed. Connect the free end to a strain insulator. 
Construct the other half of the antenna in exactly the 
same manner. 

(6) Construct each additional lower frequency 
antenna by adding more Wire W-1 to the antenna 
already formed. Each antenna length should -be 
measured from the center of the coaxial connector to the 
end of the antenna being constructed, including the 
length of the strain insulators. 

(7) After the antenna is constructed, use the 
splice c onductors -to connect the required jumpers in 
place (A, | fig. 2 : T] for the primary operating frequency. 
Each antenna constructed will operate on the 
fundamental and odd harmonies of the fundamental 
frequency for which it is constructed. C J figure 2-1 1 
shows an assembled anten na for 2,600, 2,750, 3,100, 
and 3,900 kilohertz (kHz). | Figure 2-2~l shows that a 
fundamental antenna for 2,600 kHz may also ,be used 
for 8,300, 1 3,800, or 1 9,300 kHz. 

c. Mast AB-155(*)/U Erection. After the antenna 
has been constructed, determine the position for the 
antenna to 'be erected. A compass is required for 
accurate determination of antenna orientation. Stretch 
the assembled antenna along the ground in the desired 
position. Place the antenna in a position to allow proper 
connection of the antenna to the equipment in the shelter 
after it is raised. Plan to erect the end masts several feet 
beyond the end insulators. The center mast should be at 
the coaxial connecto r and offset 3 feet from the line of 
the antenna Kfiq. 2-51 A center mast will not be required 
if the overall antenna is less than 120 feet long. Erect 
each Mast AB-1 '55(*)/U as follows: 

(1) Place Mast AB-155(*)/U at each mast 
location and remove Cover CW-124 /GRA-4 from 
Carrying Device MX387/GRA-4 (fig. 1-171 . 

(2) Drive the stake of Mast Base AB-1 54/ U 
into the ground at the desired mast location with the 
swivel end pointing 450 from the line of the antenna (fig. 
23). If the ground is soft or sandy, place the mast base 
plate (fig. 25) on the ground and push it down firmly; 
then drive the stake of Mast Base AB-154/U through the 
hole in the mast base plate. 

(3) Align the female ends of Mast Sections 
MS-44-(*) toward the mast base. Connect the first mast 
section (fig. 23) to Mast Base AB1154/U; add the 
second and third mast sections. Place a Guy Plate 
MX378/U over the third 



2-3 



TM 11-5820-256-10 



section. Add the fourth and fifth sections; place a 
second MX478/U over the fifth section. Add three more 
mast sections, and place a third MX378/U over the last 
section. 

(4) Slip a Guy Fastener MX-379/U over each 
guy stake before it is driven into the ground. Drive a guy 
stake (back guy stake) into the ground at the junction of 
the fifth and sixth MS44-(*) (25 feet from Mast Base AB- 
1 54/U). Place the fron t and side guy stakes 90° apart as 
shown in Ifigure 2-3~l Use a guy rope to measure the 
distance between the mast base and the front and side 
guy stakes. If the ground is soft or sandy, use the 
wooden stakes 'instead of the aluminum stakes, and 
loop the guys over the stakes. 

Do not use the MX379/U's. 

(5) Fasten four Guys MX-383(*)/GRA4 to 
top Guy Plate MX-378/U, four Guys MX381 (*)/GRA-4 to 
center Guy Plate MX-378/U, and the remaining four 
Guys MX-382(*)/GRA4 to bottom Guy Plate MX-378/U. 
Fasten the guys by snapping the fastener at the end of 
each guy into one of the four holes located 900 apart on 
the MX-378/U. Next, carry the free ends of the three 
back guys to a side guy stake to measure their correct 
length, Fasten these guys to the back guy stake with Guy 
Fastener MX379/U. Connect both sets of side guys to 
their respective side guy stakes , and remove slack by 
adjusting Slide Fastener FT-9 I (fig. 2-3T1 Do not 
overtighten because the mast may bend. Keep the three 
front guys together, and stretch them along the mast 
toward the front guy stake. 

(6) Remove Halyard MX-516(*)/GRA-4 from 
the carrying device, and attach the snap fastener on the 
pulley to the unused hole in the top G uy Plate 
MX378/U. Slip the rope through the pulley ffia. 2-51 
and tie the ends of the rope near the mast base to keep 
the rope from running through the pulley when raising the 
mast. 

(7) To raise the mast Kfig. 2-41 , three men are 
required. Man No. 1 holds the front guys and pulls 
steadily on them, keeping slightly more tension on the 
top guy to bow the mast slightly while being raised. Man 
No. 2 takes a position near the mast base and holds 
Mast Base AB154/U in the designated position as the 
mast is raised. Man No. 3 stands near the top end of 
the mast and raises it as he walks toward the mast base. 

(8) Adjust the guys until -the mast is vertical. 
Whenever a guy is tightened, the opposite one may have 
to be loosened slightly to keep the mast from bowing. 



d. Antenna Raising. 

(1) If the center mast -is 'used, attach the 
fastener on Halyard M X-516Q/GR A-4 to the coaxial 
connector as shown in B J figure 2-1 1 

(2) Fasten Halyard MX-516Q/GRA-4 on each 
end mast to the antenna wire by attaching one end of a 
wire (approximately 15 inches of Wire W-1) to the end 
strain insulator, and the other end to the fastener 
assembly on Halyard MX-516 (*)/GRA-4. 

(3) Pull the antenna wire into position with 
Halyards MX-516(*)/GRA-4. Tie the rope to the mast to 
prevent the weight of the antenna wire from pulling the 
loose end of the rope back through the pulley. I Figure 2-1 

[5]shows a doublet antenna completely erected. 

e. Antenna Connection. The antenna lead-in 
should be raised off the ground on poles if possible. In 
cold weather, raising the lead-in prevents the antenna 
lead-in from freezing to the ground and, at all times, 
minimizes damage which might result from lying on the 
ground. In addition, the antenna lead-in should be taped 
to both the mast and the shelter to relieve the tension on 
the coaxial connector. 

(1) Transmitting. Disconnect Cable 
Assembly, Radio Frequency CG-1333/U from the 
OUTPUT receptacle on the matching unit and the 
terminal posts on the tuning unit. Pass the antenna lead- 
in through the feedthrough in the rear wall of the shelter, 
and connect it to the OUTPUT receptacle on the 
matching unit; use Radio Frequency Adapter UG-27C for 
coupling. 

(2) Receiving. Disconnect Radio Frequency 
Cable Assemblies CG-718A/U (8 ft) from the 
UNBALANCED receptacles on the receivers. 
Disconnect Radio Frequency Cable Assembly 
CG718A/U (24 ft) from the BALANCED receptacle on the 
receiver. Pass the antenna lead-ins through the 
feedthrough in the forward wall of the shelter, and 
connect them to the BALANCED receptacles on the 
.receivers. Use Adapter Connectors UG-97'1/U as 
couplings. 

f. Other Antenna Installation. If there is not 
enough time to erect the masts, construct a semifixed 
installation by using materials other than those supplied 
as a support for the antenna wire. 

Antenna supports can be improvised by using poles, 
trees, buildings, or other suitable supports whenever 
possible. The doublet antenna must always be 'insulated 
from its supports. 

g. Erection of Doublet Antenna Using T ripod 
Adap tor Mast AB-1089/U. The tripod mast adaptor [(figl 
12-101 was designed to provide a stable antenna mast 
which can be erected quick 



2-4 



TM 11-5820-256-10 



SPUCE FASTENER ASSEMBLY. 

CONDUCTOR 



HALYARD MX-S6(*)/GRA-4 
COAXIAL CONNECTOR 



STRAIN INSULATOR 



L 



rt^O~0^ 



CONNECTOR BURNDY 
TYPE KS-90 

A. DETAILS SHOWING JUMPER 
IN SHORTED POSITION. 




RF CABLE ASSEMBLY 

CG-692/U 



B. ANTENNA CENTER DETAIL AT CENTER MAST. 



2600 KC 




HALYARD 

MX-5l6(*)/GRA-4 



JUMPERS IN 
SHORT POSITION 



C. ASSEMBLED ANTENNA 



HALYARD 
MX-5I600/GRA-4 



TM5820-256-IO-2 



Figure 2- 1 . Construction and assembly of doublet antenna. 

2-5 




Figure 2-2. Graph of antenna length versus frequency. 



ly. The assembled mast lffig. 2-11 1 is inherently stable. 
A doublet antenna erected on level ground with three 
such masts can withstand winds of approximately 25 
miles per-hour without the use of guy lines. Parts of 
Mast, AB-155(*)/U furnished with Radio Set AN/GRC- 
.26D are used for the tripod mast. To obtain full mast 
height, one additional Mast Section, MS-44 for each 
Mast, AB-155(*)/U is required. To erect a doublet 
antenna using three tripod masts proceed as follows: 

(1) Join six Mast Sections MS-44 into three two- 
section lengths. 



(2) Insert a two-section length into each of the 
adaptor legs. 

(3) Join three mast sections together inserting a guy 
plate between the upper two sections and insert the 
lower end of this asse mbly into th e hole in the upper 



2-11 



deck of the mast adapter |(fig. 

(4) Place a standard guy plate over the top mast 
section. 

(5) Attach a pulley and halyard to the top guy plate. 
Attach three guy lines to the lower guy plate. 

(6) Repeat the above until three tripod masts are 
completed. 



Change 2 2-6 



TM 11-5820-256-10 



FRONT 

our 

STAKE 



• 2S-0" 



NOTE: 

FASTENERS MX-379/U ARE PUT 
ON 4 GUY STAKES BEFORE 
DRIVING INTO GftOUNO. 




HALYARO 
MX-SI6<*)/GRA-4 



GUY MX-583W0/GRA-4 
GUY MX-38I0O/GRA-4 
GUY MX-M2W/GRA-4 



ISLIDE FASTENER 
FT- 9 



TMMCO-tM-IO-S 



Figure 2-3. Preparing Mast AB-155(*)U for erector 



(7) Prepare the antenna as shown ir | figure 2A 

m 

(8) Drive thr ee guy stak es and orient the 
tripod legs as shown in I figure 2-12.1 Six remaining guy 
stakes can be driven when time permits. 

(9) Connect the halyard of th e center mas t to 
the fastener assembly as shown at B o 1 figure 2"T| and 
hoist to full elevation. Allow the three guy lines 
connected to the lower guy plate to hang free. 

(10) Secure center guy lines to center guy 

stakes. 

(11) Connect the halyards of the end masts to 
the ends of the doublet. 

(12) Hoist both end masts simultaneously and 
tie into guy stakes. Allow the three guy lines attached to 
the lower guy plate of each mast to hang free. 



(13) Complete antenna connections as 
described in paragraph e above. The antenna 
installation as described above is inherently stable. 
Stability should be enhanced, however, as soon as 
convenient by driving the additional guy stakes shown in 
I figure 2-12~| and connecting the guy lines as indicated. 

2-7. Installation of Fuses and Batteries 

a. Shelter. 

(1) The operating equipment is installed within 
the shelter. Check to see that all operating equipment is 
firmly in place. 

(2) Make sure that the correct fuses are 
installed in the equipment. The equipment may fail if 
fuses other than those specified are used. The chart 
below lists the fuses used in each component. 



Change 2 2-7 



TM 11-5820-256-10 



Equipment Fuse 

Transmitter, Radio T-368 (')/URT F1 

F2 

Modulator, Radio MD-239(*)/GR F1 

F2 

Teletypewriter TT-98(*)/FG F1 

F2 
F4 

Reperforator-Transmitter, Teletype- F1 
writer TT-76/GGC 
or 

Reperforator-Transmitter, Teletype- F1 
writer TT-76A/GGC F2 
or 

Reperforator-Transmitter, Teletype- F1 
writer TT-76B/GGC F2 



Rating 
(amperes) 



Location 



6 
3 

1 1/2 
1 1/2 
2 

1/4 

1/16 

1.6 



1.6 
1.6 



2 
2 



Front panel of power supply deck. 
Front panel. 

Behind right cover door. 
Below door above power supply. 
Behind left cover door. 
Under dust cover. 



Under dust cover. 



Under dust cover. 



(3) Telephone Set TA-43/PT or Telephone 
Set TA-312/PT requires two Batteries PA-30 (not 
supplied with the radio set). For battery installation 
instructions, refer to the technical manual for the 
particular equipment (app A). 

b. Power Unit. Examine the storage battery in the 
power unit, Instructions for preparing the battery for 
service are attached to each battery. Follow instructions 
carefully. 



2-8. Installation of Operator Chairs 



Centrally locate the two operator c hairs in 
three teletypewriter tables (A and B, l fig. 
web straps for each chair, and strap the 



front of the 
H] Use two 
chairs in 



p osition; us e the three floor anchors as tie points (C and 



D J fig. 2-6) 



2-9. Connections 

a. Primary Power. The shelter contains 
permanently wired power outlets that provide ac power to 
the components of the radio set. When Switch Box SA- 
331 /U is 'supplied with the power unit, connect 12-foot 6- 
inch Power Cable Assembly CX-6485/U between the ac 
power receptacle at the rear of the shelter and the 
OUTPUT receptacle of the SA-331/U. Two Power Cable 
Assemblies CX-2254/U are connected from the INPUT 
receptacles of the SA-331/U to the ac outlet terminals on 
the power unit. The SA-331/ U GND terminal is 
connected to the frame of the grounding system in the 
trailer. If the power unit is operated more than 12 feet 
from the shelter, insert extension Power Cable Assembly 
CX-I166/U between the CX-6485/U and the shelter. 
When Junction Box J-85/G is used with 



the power unit instead of the SA-331 /U, connect Power 
Cable Assembly CX-1 165/U between the J-85/G and the 
shelter. When the power unit must be more than 12 feet 
from the shelter, insert an extension Power Cable 
Assembly CX1166/U between the CX-1 165/U and the 
shelter. 

Connect the cords from the J-85/G to the power unit. 
b. Grounding. 

(1) A grounding system Iff ig - 



_2^7J 



is 

permanently installed along the shelter walls and is an 
integral part of the shelter. The tuning unit, fsk- 
modulator, and transmitter are grounded with a ground 
strap from the ground bus to a mounting stud on the top 
of the transmitter. Ground straps also connect the right 
side panel of the storage cabinet and the equipment 
cabinet. A ground strap connects the matching unit to 
the ground bus. At the left of the transmitter, a ground 
strap assembly is attached to the primary power conduit, 
which places the housings of all ac outlets at ground 
potential. 

(2) The reperforator is grounded through the 
ac power cord shield to the ac outlet housing. The 
spade lug, terminating the shield, is attached to the 
existing retaining screw on the ac outlet. The ac power 
cord shield of each page printer is attached directly to the 
ground bus (fig. 2-7) . Teletypewriter tables are 
automatically placed at ground potential when they are 
secured to the shelter wall (and ground bus) with the 
rotolock fasteners. 

(3) Place the shelter grounding s stem at 
earth potential by using the ground rod and the electrical 
lead. Drive the ground rod into the earth. Clamp one 
end of the electrical lead to the 



2-8 



TM 11-5820-256-10 



ground rod, attach the ground rod, and attach the free 
end of th e lead to the shelter external ground connector 

EMZHJ- 

(4) When the shelter must be stationed over a 
soil 'having a very low conductivity, treat the soil to 
reduce its resistance. The soil can also be treated with 
substances that are highly conductive when in solution. 
Some of these substances, listed in order of preference, 
are: sodium chloride (common salt), calcium chloride, 
and magnesium sulphate (Epsom salt). The amount 
required depends on the type of soil and its moisture 
content. 

c. Interunit Cabling Iffig. 5-1 I and l 5-2~P The 
AN/GRC-26D is shipped with all interunit cabling 
complete. Check to see that the cable connectors and 
plugs are securely connected prior to operating the 
equipment. 

d. Remote Site. The application of teletypewriter 
equipment at the remote site varies bec ause of its 
flexibility. A typical remote site is shown in I figures 2-8I 

land 2-9J 

(1) One-way reversible and duplex operation 
at the remote site is possible by use of the remote 
control unit and telephone and teletypewriter equipment. 
The .remote site 'is connected to the radio set by field 
wire (not supplied with the radio set). The telephone 
and teletypewriter equipment for the remote site is not 
supplied with the radio set. 

(2) Connection of wire pairs between the 
remote site and the shelter is illustrated in TM 1 1-5820- 
256-lo rficiures 2-8 l an d 2-9. 1 For proper operation, wire 



polarity must be observed between the control unit and 
the remote control unit. It is not necessary to observe 
,wire polarity between the telephone and the remote 
control unit. 

(3) Bring the wires into the shelter through the 
feedthrough above the control unit, and con nect them to 
their res pective binding posts as shown in l figures 2-8I 

land 2-9J 

(4) Remote operation is generally intended for 
distances up to 10 miles. Greater distances will result in 
increased losses that cannot be compensated. All 
normal remote operation may be accomplished -then 
the remote si te is cabled to c ompo nents in the shelter 
as shown in l figures 2-8 l and l"2-9 l and th e remaining 
shelter c omponents are cabled as shown in l figures 5-1 1 

land 5-2J 

2-10. Initial Adjustments 

a. Certain installation and preoperational checks and 
adjustments must be made to the power unit, converter, 
page printers, and reperforator during installation of the 
AN GR C-26D. Refe r to the applicable technical manual 
listed in lappendix A | for a description of these checks and 
adjustments. 

b. Adjustments to the receivers and transmitter 
normally are performed only during' a change in 
operating frequency. 

c. The fsk-modulator, remote control unit, and control 
unit do not require any initial adjustments. 



2-9 



TM 11-5820-256-10 



3 




LINE OF ANTENNA 

TM5820-236-I0-3B 

Figure 2-4. Revising assembled Mast AB -155(*)/U. 



2-10 



TM 11-5820-256-10 




NOTE: 

THE MAST BASE PLATE IS 
USED ONLY WHEN GROUND 
IS SOFT OR SANDY. 

TMM20-2M-I0-4 



Figure 2-5. Doublet antenna, erection completed 



2-11 



TM 11-5820-256-10 




Figure 2-6. Installation of operator chairs. 



2-12 



TM 11-5820-256-10 



GROUND STRAP 
TO WING NUT OF 
TRANSMITTER, RADIO 
T-368W/URT 



1 15 V 
60 CPS 
POWER INPUT 



GROUND STRAP 
TO WING NUT OF 
STANDING WAVE RATIO- 
POWER METER 
ME-I65/G 



II5V.60CPS GROUND BOS 




REPERFORATOR-TRANSMITTER. , 
TELETYPEWRITER TT-76W/GGC | 
GROUND POINT 




□DO 

DDO 



GROUND STRAP 
TO SIDE PANEL SCREW OF 
CABINET,. ELECTRICAL 
EQUIPMENT CY-I807/G 



GROUND STRAP 
TO WING NUT OF 
CABINET, STORAGE 
CY-I72IW/GRC 



GROUND STRAP 
ASSEMBLY 
CLAMPED 
TO CONDUIT 



ELECTRICAL LEAD 



GROUND ROD 



TM5820- 256-10-6 



Figure 2-7. Shelter, Electrical Equipment S-56(*)/G, primary power and grounding system 

2-13 



TM 11-5820-256-10 




6 l 6 



• TELEPHONE SET 

I TA-43/PT , 

I J 

REMOTE SITE NOTE: 

CONNECTIM WIRE RETWEIR THE amOUW POSTS Of 
CONTROL, RMXO SET C-II2VMC.COHTROL. REMOTE 
SWITCHMG C-I4JH/ORCAIO TELEPHONE SET T4-4S/PT 
13 WIRE W-l. 

TMMZO-CM-lO-3* 



Figure 2-8. Typical remote site intercabling diagram. 
2-14 



TM 11-5820-256-10 



Figure 2-9. Remote site cabling diagram (modified per MWO 1 1-5820-256-35/1). 

(Located in back of manual) 
2-15 



TM 11-5820-256-10 




2-17 



TM 11-5820-256-10 




2-18 



TM 11-5820-256-10 




B. TRIPOD AND STAKE ORIENTATION. ei_582o-256-io- cz- tn- i 



Figure 2-12. Doublet antenna installation, using Tripod Adapter, 
MastAB-1069/U 
Change 2 2-19 



CHAPTER 3 
OPERATING INSTRUCTIONS 



TM 11-5820-256-10 



WARNING 

Before operating this equipment, make certain all requirements of TB SIG 291 are met. Injury or death 
could result from improper or careless operation. 



Section I. OPERATOR'S CONTROLS AND INDICATORS 



3-1. Damage from Improper Settings 

a. Haphazard operation or improper setting of 
the controls can cause damage to the equipment; 
therefore, knowledge of the function of every con- 
trol is important. 

CAUTION 

Be particularly careful when tuning the 
transmitter; improper tuning will damage 
the output radio frequency (rf) coils. 

b. When the matching unit control switch is set to 
POWER, ADJUST, or SWR, full transmitter output is 



dissipated in the dummy load of the matching unit. Do 
not apply power contentiously for longer than 1 minute. 
The matching unit may be damaged by the great amount 
of heat generated. 

3-2. Modulato r, Radio MD-239(*)/GR Control and 
Indicator tfiq. 3-1t 

The chart below lists the controls and indicator of the fsk- 
modulator and indicates their functions. 



Control or indicator Function 

POWER switch Applies ac power to the fsk-modulator when set to ON. 

BAND SELECTOR switch An eight-position switch that determines the amount 

of frequency shift. Set to the band that includes the 
frequency to which the transmitter is tuned. 
Sw pos Amount of frequency 





shift (Hz) 


1.5-2 


850 


2-3 


850 


3-4 


425 


4-6 


425 


6-8 


212.5 


8-12 


212.5 


12-16 


106.25 


16-20 


106.25 



Pilot lamp indicates the presence of ac power. 



3-3. Control, Radio Set C1 123/GRC Controls, Indicator, and Jack s! (fiq.~3 : 3 . l3-3.l an d 5-1)1 

The chart below lists the controls, indicator, and jacks of the control unit and indicates their functions. 



Control, indicator, or Jack Function 



Power switch Applies ac power to the control unit when set to ON. 

SIDETONE switch A three-position switch that connects the transmitter 

sidetone to either receiver. 

Sw pos Transmitter sidetone 

REC A (or RCVR A) Applied to receiver A. 

OFF Terminated in control unit 

RECB (or RCVR B) Applied to receiver B. 



3-1 



TM 11-5820-256-10 



Control, indicator, or Jack 



Function 



REMOTE TEL switch . 



HYBRID BAL control. 
TELETYPE switch 



, A three-position switch that connects the shelter and 

remote site telephone equipment together and to the 
transmitter and receiver 

Sw pos Telephone equipment 

connections 

REC A (or RCVR A) Connects the transmitters 

of the shelter and e- 
mote site telephone equip- 
ment to the transmitter. 
Connects the receivers of 
the shelter and remote 
site telephone equip- 
ment to receiver A. 

LOCAL TEL Connects the shelter and 

remote site telephone 
equipment together. 

REC B or RCVR B Connects the transmitters 

of the shelter and re; 
mote site telephone 
equipment to the trans- 
mitter. Connects the ret 
ceivers of the shelter and 
remote site telephone 
equipment to receiver B. 
, Adjusts the signal level between the shelter's TA- 

31 2/PT and the transmitter. 
. A four-position switch that connects the teletypewriter equipment 

for normal or remote and one-way reversible or duplex operation. 



Swpos 
NORMAL OW 



NORMAL DX 



REMOTE OW 



REMOTE DX 



Pilot lamp 

REC DX jacks . 



ONE WAY OR SEND DS jacks 



Type of operation 
Connects the shelter's tele- 
typewriter equipment for 
one-way reversible opera- 
tion. 

Connects the shelter's tele- 
typewriter equipment for 
duplex operation. 
Connects the remote tele- 
typewriter equipment 
for one-way reversible 
operation. 
Connects the remote tele- 
typewriter equipment 
for duplex operation. 

Indicates the presence of ac power. 

, Two black and four red jacks. The two black jacks 

are not connected. The four red jacks are conneced 
in series and will route the received teletypewriter 
signals to the receive teletypewriter equipment dur- 
ing duplex operation. 

, Two black and two red jacks. The two black jacks are 

connected in series and route the transmitted tele- 
typewriter signals from the transmit teletypewriter 
equipment to the fsk-modulator and to the red jacks 
The two red jacks are connected in series and route 
the transmitted teletypewriter signals to the receive 
teletypewriter equipment for local copy preparation. 
The two red jacks also route the received teletype- 
writer signals to the receive teletypewriter equipment 
during one-way reversible operation. 



3-2 



TM 11-5820-256-10 



Control, indicator, or Jack Function 

TD jack the transmit lead from the transmitter- 
distributor of the reperforator. Connected in series 
with the two black ONE WAY OR SEND DX jacks. 

BIAS ADJUST control Adjusts loop current to teletypewriter equipment. 

Loop current meter Indicates value of bias current. 

POWER ON-OFF switch Applies dc power to teletypewriter equipment when 

set to ON. 

AC PWR connector Provides for input connection of ac power cable. 

DC PWR connector Provides for output connection of dc power cable. 



3-4. Minor Component Controls, Indicators, and 
Jacks 



a. Control Remote Switching C- 474/GRC\n\cT\ 

11-11 1 and l 1-121 . The remote control unit contains an 
external toggle switch labeled XMTR ON. When proper 
connections have been made between the radio set and 
the remote control unit, the transmitter will be keyed 
when the switch is set to XMTR ON. Four sets of 
terminals are provided for termination of remote 
teletypewriter equipment and marked as follows: ONE 
WAY OR SEND, REMOTE TEL, REC DX, and LOCAL 
TEL. Control, Remote Switching C-1474/GRC, as 
modified per MWO 115820-256-35/1, provides three 
jacks and two connectors for termin ation of remote 
teletypewriter equipment tfig. 2-9)7! The jacks are 
marked ONE WAY OR SEND DX, REC DX, and LOC 
TEL. The connectors are marked TTY SWITCH and 
REMOTE. 

b. Loudspeaker Assembly LS-206(*)/U ffig. 1-41 . 
The speaker assembly contains two external toggle 
switches labeled ON CHANNEL A and ON CHANNEL B, 
respectively. The ON CHANNEL A switch allows audio 
signals to be received from the channel A receiver when 
placed in the on (up) position. The ON CHANNEL B 
switch performs a similar function for the channel B 
receiver. 



Switch Box 
two-position 'switch 



c. Blower Assembly, Electrical HD-223/( Iffia. 1-1 
[4] . Blower Assembly, Electrical HD223/G contains an 

external toggle switch which controls ac power to the 
blowers. When the switch is set to ON, the two blowers 
inside the unit are activated. The pilot lamp indicates the 
presence of ac power. 

d. Switch Box SA-331/uWq. 
SA-331/U contains an external 
labeled NO. 1 and NO. 2 and is used to switch from one 
Generator Set, Gasoline Engine PU-286/G to another. 
When the switch is set to NO. 1 , power for the shelter is 
drawn from the PU-286/G designated No. 1 . When the 
switch is set to NO. 2, power for the shelter is drawn 
from the PU-286/G designated No. 2. 

e. Junction Box J-2597/GRC [T\q. 1-8)| Junction 
Box J-2597/GRC provides through connections when 
the radio set is used for the transmission and reception 
of clear text. During transmission and reception of 
encrypted traffic, the cables connected to the junction 
box are removed and connected to the crypto equipment 
and the junction box is not used. 

f. Junction Box J-2598/GRC |(fig. 1-8)| Junction 



Box J-2598/GRC provides through connections when the 
radio set is used for the transmission and reception of 
clear text. During transmission and reception of 
encrypted traffic, the cables connected to the junction 
box are removed and connected to the crypto equipment 
and the junction box is not. 



3-3 



PILOT LAMP 



TM 11-5820-256-10 



©J) M.O. IN 



o 




(fuse I 
1. 5 AMP 



<s> 



C 



BAND 
SELECTOR 
4-6 6-8 
3-4 I I 8-IZ 



9- 



=3 



l»ERI»L NO. I 
ORDER KQ I ~1 
Ifr M == 



2-3- 
1.5-2- 




12-16 
16-20 



f©M FSK OUT 



ON 



POWER 



OFF 




1.5 AMP 
CRYSTAL OVEN 



NOTE: 

ON MODULATOR. RADIO MD-239/GR, THE POWER SWITCH IS LOCATED BETWEEN THE FUSES 

' TM5820-256- 10-8 



Figure 3-1. Modulator, Radio MD-239(*)/GR, front panel controls. 



3-4 



TM 11-5820-256-10 




PILOT LAMP 



POWER SWITCH 



RAOO SET COHtTROL C -lgMjRC 
I SERIAL NO. I 



ORDER NO. I 



IIS VOLTS AC 50-60 CYCLES 




OFF 



OFF 

REC A v REC B 




LOCAL 
TEL 

REC A , REC B 




SIQETONE 



HYBRID BAL 



REMOTE TEL 



DX OW 

— OW OX- 




NORMAL >*V' i REMOTE 
TELETYPE 



NOTE: 

ON CONTROL, RADIO SET C-II23/GRC BEARING ORDER NO. 25209-PHILA-54, 
PANEL MARKINGS DO NOT APPEAR AT ON- OFF SWITCH 

TM5820-256-I0-9 



Figure 3-2. Control, Radio Set C- 1 123/GRC, front panel controls. 



3-5 



TM 11-5820-256-10 




TMM20-256-IO-9Q 

Figure 3-3. Control, Radio Set C-1 123/GRC (modified per MWO 1 1-5820-256-35/1), 

front panel controls. 



3-6 



TM 11-5820-256-10 



SECTION II. OPERATION 



3-5. Types of Operation 

a The radio set may be operated locally (from the 
shelter) or from a remote site. Remote operation is 
possible through the use of the remote control unit. 
Either duplex or one-way reversible (half duplex) 
operation may be used. When the radio set is in motion, 
one-way reversible (half duplex) operation is normally 
used. When the radio set is at halt, either one-way 
reversible (half duplex) or duplex operation may be 
employed. Doublet antennas can be erected to provide 
additional operating range. 

b The radio set is used primarily as a radio 
teletypewriter station. AM voice or cw operation is 
available if required. 

3-6. Preliminary Starting Procedure 

Preset the controls as described below before attempting 
to operate the equipments. 



Component Control Position 

Power unit Circuit breakers OFF 

Shelter Circuit breakers OFF 

Transmitter FILAMENT POWER 

circuit breaker OFF 

PLATE POWER 

circuit breaker OFF 

TUNE-OPERATE switch 
(TUNE-NORMAL 
switch on some models)TUNE 
PLATE RELAY switch ... OFF 
KEYING CONTINUOUS- 
NORMAL switch 
(EXCITER PLATE 
POWER switch on 

some models) NORMAL (OFF 

on some models) 

Matching unit Function switch POWER 

Adjust control COUNTER- 
CLOCKWISE 

Fsk-modulator POWER switch OFF 

Control unit POWER switch OFF 

BIAS POWER ON-OFF OFF 
Converter POWER switch 

(under Channel A) OFF 

Each receiver FUNCTION switch OFF 

Speaker assembly CHANNEL A OFF 

CHANNEL B OFF 

Blower Assembly, 
Electrical 

HD-223/G POWER switch OFF 

Reperforator POWER switch OFF 

LIGHT switch OFF 

SEND-LOCK switch LOCK 

Page printer MOTOR switch OFF 

LIGHT switch OFF 

SEND-LOCK switch LOCK 

3-7. Starting Procedure 

With the controls set as outlined in l paragraph 3-6I 



Preliminary Starting Procedures, perform the procedures 

indicated below to apply power to the equipment. 

Component Control Position 

Power unit START button Press START- 

STOP switch to 
START position 
and release when 
engine oil pres- 
sure reaches 20 
PSI. 

Switch Box SA-331 POWER SUPPLY switch NO. 1 or NO. 2 

depending on gen- 
erator in use. 

Power unit Circuit breaker ON 

Shelter Circuit breakers ON 

Transmitter FILAMENT POWER 

circuit breaker ON 

FILAMENT VOLTAGE 
control Adjust for a read- 
ing of 5 to 5.2 on 
FILAMENT 
VOLTAGE meter. 

Fsk modulator POWER switch ON 

Control unit POWER switch ON 

BIAS POWER switch .... ON 

Blower Assembly 
Electrical 

HD-223/G POWER switch ON 

Speaker assembly Desired CHANNEL 

switch ON 

Each Receiver 
R-390(*)/ 

URR FUNCTION switch AGC 

Converter POWER switch ON 

NOTE 

For one-way reversible (half duplex) 
operation, only one receiver is normally 
in use. The remaining receiver is preset 
for possible emergency use in full duplex 
operation. 

3-7.1. Presetting and Calibration Procedures 

With the controls set as indicated in l paragraph 3-7J 
perform the following procedures: 

a Presetting Receiver and Converter. 

Component Control Position 

Converter AFC switch OFF (under. 

Channel B) 

AFC SHIFT 

ADJUSTMENT Set to 

AFC THRESHOLD 

LEVEL OFF 

CHANNEL 

SELECTOR A or B (determined 

by receiver 
in use) 

MARK HOLD-XTAL 

AFC switch MARK HOLD 

DRIFT INDICATOR Set to O 



Change 4 3-7 



TM 11-5820-256-10 



Receiver LINE METER switch OFF 

LINE GAIN Set to 

ANTENNA TRIM Set to 

AGC FAST 

LIMITER OFF 

AUDIO RESPONSE SHARP 

BREAK IN switch OFF 

BANDWIDTH switch 0.1 KC 

BFO PITCH Set to 

BFO ON 

DIAL LOCK Fully 

counterclockwise 
(ccw) 

ZERO ADJUST Fully ccw 

LOCAL GAIN Set to 

RF GAIN 10 

KILOCYCLE 

CHANGE Set to assigned 

frequency 

MEGACYCLE 

CHANGE Set to assigned 

frequency 

b Receiver Calibration. 

Component Control Position 
FUNCTION switch CALIBRATE) 



LOCAL GAIN Set to comfortable listening level 

KILOCYCLE CHANGE ..100 KC setting closest to 
assigned frequency 

ZERO ADJUST Fully clockwise 

KILOCYCLE CHANGE ..Adjust for zero beat 

Component Control Position 

NOTE 

It may be necessary to change the 
AUDIO RESPONSE switch to WIDE and 
to increase the setting of the 
BANDWIDTH switch to obtain a zero 

beat. 

Component Control Position 

ZERO ADJUST Fully ccw 

FUNCTION switch AGC 

KILOCYCLE CHANGE Set to assigned frequency 

BANDWIDTH KC switch ...8 

LOCAL GAIN Set to 

AUDIO RESPONSE switch ..WIDE 

c Presetting Control Unit. 

Component Control Position 

SIDETONE switch OFF 

HYBRID BALANCE switch Arrow is pointing upwards 

REMOTE TEL switch LOCAL TEL 

TELETYPE switch NORMAL-OW 

d Switch SA-12J3/GRC. The SA-1253/GRC 

SECURITY INSTALLED-REMOVED switch is set to the 

applicable position indicating the security (crypto) 

equipment is REMOVED or INSTALLED. 



e Fsk-Modulator. The fsk-modulator BAND 
SELECTOR switch is set to the band corresponding to 
the assigned operating frequency. 

/ Transmitter Presetting and Calibration. 

Component Control Position 

600 OHM LINE GAIN Fully ccw 

CARBON MIKE GAIN Fully ccw 

MODULATOR BIAS Fully ccw 

SERVICE SELECTOR switch. ..FSK 

BAND SELECTOR switch Set to band corresponding to 

assigned frequency 

TUNING CONTROL Set to assigned frequency 

EXCITATION METER SWITCHPA GRID X2 

PA BAND SWITCH Set to band corresponding to 

assigned frequency 

POWER AMPLIFIER 

LOADING 28.0 

POWER AMPLIFIER TUNING Set in accordance with CALI 

g Tuning Unit Presetting and Calibration. 

Component Control Position 

FREQUENCY INCREASE See CALIBRATION CHART 

on side of the transmitter 
(orinTM 11-80910) 

COUPLING See CALIBRATION CHART 

RANGE Switch See CALIBRATION CHART 

NOTE 

When operating in the 10 to 20 MHz 
range, the LOW FREQUENCY 
INCREASE control for the 2 to 10 MHz 
range must be set to 30.0 

3-8. Tuning Procedures 

With the controls set as described in | paragraph 3-7.1 1 
perform the procedures in subparagraph a below to tune 
the transmitter when using a whip or long wire antenna. 
Perform the procedures in subparagraph b below for a 
doublet antenna. 

NOTE 

In the unlettered model transmitter, the 
KEYING switch is labeled EXCITER 
PLATE POWER and the NORMAL and 
CONTINUOUS positions of the KEYING 
switch correspond to OFF and ON 
respectively. In the A or C model 
transmitter procured on Order No. 
28459-Phila-55, the TUNE-OPERATE 
switch is panel marked, TUNE- 
NORMAL. The NORMAL position 
corresponds to the OPERATE position. 
a Tuning Procedure With Whip or Long-Wire 
Antenna. 

(1) Set KEYING CONTINUOUS-NORMAL 
switch on the transmitter to KEYING CONTINUOUS. 
(EXCITATION meter should read upscale). 

(2) Set LOCAL GAIN control on receiver to a 
comfortable listening level. 



Change 4 3-8 



(3) Set BANDWIDTH KC switch on receiver to 0.1 
and the AUDIO RESPONSE control to SHARP. 

NOTE 

If difficulty in zero beating is 
encountered, set BANDWIDTH KC 
switch to 8 and the AUDIO RESPONSE 
control to WIDE. 

(2) Adjust the TUNING CONTROL on the 
transmitter until a zero beat is heard in the speaker. The 
transmitter frequency is now the same as that indicated 
on the frequency indicator on the receiver, regardless of 
any small difference from the transmitter dial indication. 

(3) Set the KEYING CONTINUOUS-NORMAL 
switch on the transmitter to NORMAL. 

(6 Set the LOCAL GAIN control on the receiver to 0. 
CAUTION 

The receiver will be damaged if the 
BREAK IN switch is left in the OFF 
position. 

(7) Set the BREAK IN switch on the receiver to ON. 

(8) Set the PLATE POWER circuit breaker on the 
transmitter to ON. 

(9) Set the PLATE RELAY switch on the transmitter 
to the up position. 

(10) Set the KEYING CONTINUOUS-NORMAL 
switch on the transmitter to CONTINUOUS. 

CAUTION 

When the matching unit control switch is 
set to POWER, ADJUST, or SWR, full 
transmitter output power is dissipated in 
the dummy load of the matching unit. 
To avoid damage to the unit, do not 
apply power continuously for longer than 
10 minutes. 

(1 1 ) Adjust the POWER AMPLIFIER TUNING control 
on the transmitter for a "dip" (minimum) on the PA 
PLATE meter. 

(12) Adjust the POWER AMPLIFIER LOADING 
control on the transmitter clockwise for a reading of 150 
ma on the PA PLATE meter. 

(13) Adjust the POWER AMPLIFIER TUNING control 
on the transmitter counterclockwise for a "dip" 
(minimum) on the PA PLATE meter. 

(14) Adjust the POWER AMPLIFIER LOADING 
control on the transmitter clockwise for a reading of 150 
ma on the PA PLATE meter. 

(1 5) Repeat steps (1 3) and (1 4) until a reading of 1 50 
ma is attained and no "dip" is observed when the 
POWER AMPLIFIER TUNING control only is turned 
counterclockwise. 

NOTE 

The matching unit meter indicates the 
amount of power produced by the 
transmitter. 



TM 11-5820-256-10 

(16) Set the KEYING CONTINUOUS-NORMAL 
switch on the transmitter to NORMAL. 

(17) Set the TUNE-OPERATE switch on the 
transmitter to OPERATE. 

(18) Set the KEYING CONTINUOUS-NORMAL 
switch to CONTINUOUS. 

(a) The FILAMENT VOLTAGE meter should 
indicate 5 to 5.2 volts. 

(b) The EXCITATION meter should indicate a 
reading of 8 milliamperes minimum. 

(c) Turn the EXCITATION METER SWITCH 
to the INT AMP PLATE X10 position. The EXCITATION 
meter reading should be between 20 and 70 ma. 

CAUTION 

Current in excess of 70 milliamperes will 
cause damage to the I PA tube and 
greatly reduce it's life expectancy. 

(1 9) Adjust the POWER AMPLIFIER TUNING control 
on the transmitter to obtain a minimum reading on the 
PA PLATE meter. 

(20) Adjust the POWER AMPLIFIER LOADING 
control for a reading of 350 ma. 

(21 ) Repeat steps (1 9) and (20) until a reading of 350 
ma is attained and no "dip" is observed when the 
POWER AMPLIFIER TUNING control is turned. 

NOTE 

A maximum indication on the PA PLATE 
meter should not exceed 350 ma for CW 
or FSK operation and 275 ma for AM. 
VOICE or FSK-AM. operation. 

(22) Set the KEYING CONTINUOUS-NORMAL 
switch to NORMAL. 

(23) Set the control switch on the matching unit to 
ADJUST. 

(24) Set the transmitter KEYING CONTINUOUS- 
NORMAL switch to CONTINUOUS. 

(25) Turn the ADJUST control on the matching unit to 
obtain a full scale reading of 600 or a maximum if the 
600 is not obtainable. 

(26) Set the transmitter KEYING CONTINUOUS- 
NORMAL switch to NORMAL. 

(27) Set the control switch on the matching unit to 
SWR. 

(28) Set the transmitter KEYING CONTINUOUS- 
NORMAL switch to CONTINUOUS. 

(29) Adjust the FREQUENCY INCREASE control on 
the tuning unit (TN-339/GR) to obtain a minimum reading 
on the meter of the matching unit. 

(30) Adjust the COUPLING control on the tuning unit 
to obtain a minimum reading on the meter of the 
matching unit. 

(31) If a minimum reading at this time is not in the 
green area of the matching unit meter, repeat steps (29) 
and (30) alternately until a green area reading is 
obtained. 



Change 4 3-9 



CAUTION 

If the transmitting antennas of two or 
more radio sets are close together, 
coordinate tuning operations so that one 
set is not transmitting while the control 
switch of the matching unit in the other 
set is in the SWR position. Power 
radiated from a nearby antenna can 
cause damage to resistors in the 
matching unit. 

NOTE 

If the minimum swr is 1.5 to 1 or higher, 
check for loose connections and make 
sure that the roller contacts in the tuning 
unit are clean. At frequencies above 17 
MHz, if a 1 :1 swr cannot be obtained, 
remove the top antenna section and 
readjust the tuning unit. 

(32) Set the transmitter KEYING 
CONTINUOUS-NORMAL switch to NORMAL. 

(33) Set the control switch on the matching unit 
to OPERATE. 

NOTE 

Minor readjustment of the transmitter 
POWER AMPLIFIER TUNING and 
POWER AMPLIFIER LOADING controls 
may be necessary to obtain a PA PLATE 
meter indication of 350 ma for cw or fsk 
operation and 275 ma for am. or fsk-am. 
operation. 

b. Tuning Procedure with Doublet Antenna. 

(1) Follow the procedure given in 
subparagraph a(1) through (28) above. 

NOTE 

The swr cannot be corrected by 
adjusting the transmitter. The swr can 
only be improved by correcting the 
antenna length for the operating 
frequency. The formula for antenna 
length is based on average conditions. 
The antenna length may be different 
from calculated length because of 
ground conditions, antenna height, or 
proximity of trees and buildings. 

(2) Read the swr on the matching unit meter. 
It may be as high as 2:1 . If the meter indicates above 2, 
check for loose or broken connections in the antenna 
lead and make sure that the antenna is not touching 
trees, wires, or other obstructions If the meter still 
indicates above 2, the antenna must be shortened or 
lengthened physically. 

(3) If the meter on the matching unit does not 
read in the white (2:1) or green area, set the KEYING 
CONTINUOUS-NORMAL switch to NORMAL. 

(4) Lengthen or shorten the antenna. 



TM 11-5820-256-10 

(5) Recheck the swr by setting the KEYING 
CONTINUOUS-NORMAL switch to CONTINUOUS and 
read the meter. 

(6) Set KEYING CONTINUOUS-NORMAL 
switch to NORMAL 

(7) Perform (3) through (6) alternately until a 
satisfactory swr reading is obtained. 

(8) Set CONTROL switch on the matching 
unit to OPERATE. 

3-9. Operating Conditions 

One of several operating conditions can be used, 
depending on the existing situation. The radio set is 
capable of mobile or mobile-at-halt operation. 

a. Mobile Operation. In this type of operation the 
radio set is used while in motion. The tied-down whip 
antennas are used for transmission and reception of 
signals. One-way reversible operation is usually 
employed whereby the transmitter and receiver do not 
operate simultaneously. When the transmitter is used, 
the receivers (or receiver) are disabled; when the 
receivers are used, the transmitter is disabled. The 
transmitter and receivers can use the same frequency in 
this type of operation. 

b. Mobile-at-Halt Operation. In this type of 
operation, the radio set is stopped but may be moved 
again. The doublet antennas may be erected for 
transmission and reception of signals. Duplex operation 
can be used instead of one-way reversible operation. In 
duplex operation, the transmitter and receiver should 
operate on frequencies separated by at least 400 kHz. 
This separation makes it possible for the radio set to 
transmit and receive at the same time without 
interference between the transmitter and the receiver. 

c. Operating Procedures. The radio set may be 
operated either locally (within the shelter) or from a 
remote site (at a maximum distance of 10 miles). 
Operation is possible in any one of four modes: fsk fsk- 
am. am. voice, and cw. The control unit is the control 
center for the radio set. All signals to or from the 
teletypewrite equipment and from a microphone or key 
are routed through the control unit. To operate the radio 
set, start and tune t he e quipment as instructed in 
I paragraphs 3-6 t hrough ! 3-8,1 and follow the p rocedure for 
the d esired t ype of operation as discussed in lparaoraphsl 
3-10l throuoh l3-13l 

3-10. Fsk Operation 

The signals from the sending teletypewriter equipment 
pass through the security equipment or junction boxes, 
through the control unit and polar relay to key the fsk 
modulators, which in turn keys the transmitter. 
The receiving teletypewriter equipment is actuated by 
signals received from the two receivers, the converter, 
the control unit, and the secure gear or / junction boxes. 
The four-position TELETYPE switch 



Change 4 3-10 



on the control unit selects the type of teletypewriter 
operation desired. Two positions are used with local 
operation and two are used with remote operation. 

a. Fsk One-Way Reversible (Half-Duplex) 
Operation from Shelter. 

(1) Turn the security equipment power switch 
ON (if installed). 

(2) Turn the page printer (send teletype) 
MOTOR and LIGHT switch ON. 

(3) Place the SEND-LOCK switch to SEND 

position. 

(4) Adjust the BIAS ADJUST for a reading of 
60 ma on the bias meter of the control unit. 

(5) Rotate the TUNING CONTROL on the 
transmitter for maximum indication on the converter 
SIGNAL INPUT meter, and an indication of 50 to the 
right of on the converter DISCRIMINATOR meter. 

NOTE 

This requires only a very slight 
movement of the tuning control. 

(6) Activate security equipment (if installed). 

(7) Depress spring loaded LINE BREAK 
switch on the page printer to obtain a reading of 50 to the 
left of on the DISCRIMINATOR meter. If unable to 
obtain the reading of 50 to the left, recheck the 
transmitter TUNING CONTROL. 

(8) Place the SEND-LOCK switch on the page 
printer to the LOCK position. 

(9) The AN/GRC-26D is now ready to operate 
in the FSK mode of operation. In order to print an 
incoming signal it must be noted that the MARKHOLD- 
XTAL switch on the converter must be placed on the 
XTAL left position to allow the incoming signal to pass to 
the teletype equipment. 

(10) For sending a prepared tape from the 
reperforator, set the SELECTOR switch to position 1 and 
the send page printer SEND-LOCK switch to the SEND 
position. Insert the tape into the transmitter-distributor 
and operate the START-STOP-FEED RETRACT switch 
to START. The page printer and reperforator will print 
page and tape copy, respectively. The teletypewriter 
message will be transmitted. 

b. Fsk Duplex Operation From the Shelter. For fsk 
duplex operation , perfor m the tuning procedures in 

I paragraphs 3-6 1 through 1 3-8 1 before performing the 
following procedures: 

(1) Set the control unit TELETYPE switch to 
NORMAL DX. 

(2) Turn the secure equipment power switch 
(if installed) to the ON position. 

(3) Set the receive page printer MOTOR and 
LIGHT switches to ON. 

(4) Turn the reperforator POWER, LIGHT, 
and MOTOR switches to ON. 



TM 11-5820-256-10 

(5) Turn the POWER switch of the converter 
to the ON position; allow the converter to warm up. 

(6) Set the teletype SEND-LOCK switch to the 
SEND position. 

(7) Tune receiver A for the teletype signal 
following the procedures from TM 11-5820-358-10 
(R390A/URR). 

NOTE 

When operating duplex, make sure that 
the difference between the transmitter 
frequency and receiver frequency is at 
least 400 kHz. 

(8) Slowly retune radio receiver A while 
observing the channel A discriminator meter until the 
meter needle deflects to the right and to the left for 
miscellaneous keying signals. The deflections will be of 
approximately equal plus and minus values when the 
receiver is correctly tuned. The reading on the SIGNAL 
INPUT meter should be at a maximum for the station 
being tuned in. 

(9) Rotate the CHANNEL SELECTOR switch 
to position A. (10) Rotate the channel A AFC- 
XTLMARK-HOLD switch to the right or left AFC position 
corresponding to the XTAL position required for correct 
copy and immediately turn the channel A AFC SHIFT 
ADJUSTMENT until the AFC INDICATOR stops 
spinning. The teletypewriter should start printing. 

(11) Adjust the channel A AFC THRESHOLD 
LEVEL control knob to the highest clockwise reading that 
does not allow weak signals to operate the teletypewriter. 
A practical way to recognize this setting is to advance the 
control knob several divisions from the OFF position and 
check to see that the teletypewriter is printing correct 
copy. If the teletypewriter starts printing garbled copy, 
advance the control knob clockwise. The setting of the 
control knob is subject to change due to different 
transmission conditions. A steady mark conditions 
results when the transmitting station shuts down or when 
the signal level drops below the level set by the AFC 
THRESHOLD LEVEL. 

(12) If receiver B is being used, perform the 
procedures in (8) through (10) above using the B side of 
the converter. 

c. Fsk One-Way Reversible (Half-Duplex) 
Operation from Remote Site. For fsk half-duplex 
operation fr om the remote site, perfor m the tuning 
procedures ir j paragraph 3-6! through [3^8]above and the 
following: 

(1) Con nect the remote equipment to the 

shelter as shown i n! figures 2^81 oi l 2-9] 

(2) Ad just the equipment as indicated in 

I paragraph 3-11 fa and set the control unit TELETYPE 

switch to REMOTE OW. 



Change 4 3-11 



TM 11-5820-256-10 



(3) To monitor the remote site at the shelter, 
set the send page printer SEND-LOCK switch to LOCK 
and set the reperforator SEND-LOCK switch to LOCK. 
Adjust the remote site equipment as follows: 

(a) Set the teletypewriter POWER, 
MOTOR, and LIGHT switches to ON. 

(b) Set the teletypewriter SEND-LOCK 
switch to LOCK. 

(c) The radio set can now be keyed and 
un-keyed from the remote site control unit (C 
1474/GRC). The page printer will monitor both the 
received and transmitted signals. 

d. Fsk Duplex Operation from Remote Site. With 
the shelter equipment set as indicated in subparagraph c 
above, set the control unit TELETYPE switch to 
REMOTE DX. Monitoring the remote site at the shelter 
can be achieved by setting the page printer SEND-LOCK 
switch to LOCK and the reperforator SEND-LOCK switch 
to LOCK. Adjust the remote site equipment as follows: 

(1) Set the receive page printer POWER, 
MOTOR, and LIGHT switches to ON. 

(2) Set the receive page printer SEND-LOCK 
switch to LOCK. 

(3) Set the send page printer POWER, 
MOTOR, and LIGHT switches to ON. 

(4) Set the send page printer SEND-LOCK 
switch to SEND and operate from the remote site. 

3-11. Am. Voice Operation 

Fo r am. voice operati on, perf orm th e tuning procedures 
in I paragraphs 3-6 I throuqh I 3-8. I Then adjust the 
equipment as indicated below: 

a. Am. Voice Half Duplex Operation from Shelter. 

(1) Tune and adjust receiver A for a voice 
signal (see TM 11-5820-357-10 for the R-390/URR or M 
1 1 5820-358-1 for the R-390A/URR). 

(2) Connect the microphone to the MIC or 
KEY jack on the control unit (C-1 1 23/GRC). 

(3) Place EXCITATION METER switch on the 
transmitter to MOD PLATE X20. 

(4) Place SERVICE SELECTOR switch on the 
transmitter to AM. 

(5) Set PLATE RELAY switch on the 
transmitter to OFF. 

(6) Press the PUSH TO TALK switch on the 
microphone and adjust the MODULATOR BIAS control 
on the transmitter until a reading of 2.5 is obtained on the 
EXCITATION meter (50 ma.). 

(7) Speak normally into the microphone and 
adjust the CARBON MIKE GAIN control on the 
transmitter for a maximum reading of 230 ma. on the 
EXCITATION METER. If 230 ma. is not exceeded on 
the peaks, the transmitter is adjusted for 100 percent 



modulation with peak clipping control for modulation over 
100 percent modulation. 

(8) Release the PUSH TO TALK switch; the 
radio set is ready for operation. 

b. Am. Voice Duplex Operation from Shelter. To 
operate am. voice duplex, perform the procedures 
indicated in subparagraph a above, tune receiver A as 
indicated in | paragraph 3-8b (for receiving), and perform 
the following procedures. 

CAUTION 

Receiving and transmitting frequencies 
must be separated by at least 400 kHz 
to prevent damage to the receiver. 

(1) If transmission and reception from the 
telephone set is desired, set the control unit REMOTE 
TEL switch to REC A. 

(2) Press the shelter telephone set PUSH TO 
TALK switch. 

(3) Adjust the control unit HYBRID BAL 
control for the same amount of modulation at the 
transmitter as indicated in subparagraph a (6) and (7) 
above. 

(4) Release the PUSH TO TALK switch. 

(5) The received signal is heard at the shelter 
telephone set, press the PUSH TO TALK switch and talk 
into the telephone set to transmit. 

c. Am. Voice Duplex Operation from Remote Site. 
The following procedures supplement the procedures 
indicated in subparagraph b above. 

(1) Conne ct the rem ot e eq uipment to the 
shelter as indicated i n! figures 2"l3| or | 2-9.1 

(2) Set the remote control unit XMTR switch 

to ON. 

(3) Operate the remote telephone PRESS TO 
TALK switch and talk into its microphone. The remote 
telephone may be monitored on the shelter telephone 
set. The remote or shelter telephone may modulate the 
transmitter. 

(4) Adjust the control unit HYBRID BAL 
control, in the shelter, for the same amount of 
modulation at the transmitter from the remote and the 
shelter telephones. 

(5) Release the PRESS TO TALK switch; the 
radio set is ready for operation. 

d. Am. Voice Half-Duplex Operation from Remote 
Site. The following procedures supplement the 
procedures in subparagraphs b and c above. 

(1) Tune receiver A to the same frequency as 
the transmitter. 

NOTE 

The receiver is disabled during 
transmission when operating one-way 
reversible (half duplex). 

(2) Set the remote control unit XMTR ON 
switch to ON. 



Change 4 3-12 



(3) Operate the remote telephone set PRESS 
TO TALK switch and speak into the mouthpiece to 
transmit. 

(4) Set the remote control unit XMTR ON 
switch to its OFF position to receive incoming messages. 

3-12. Fsk-Am. Operation 

To operate the radio set in the fsk-a m. mode, perform 
the tuning procedures indicated in I paragraphs 3-6l 
I through 3"^9~l and then proceed as follows: 

a. Turn transmitter SERVICE SELECTOR switch to 
FSK-AM. 

b. Adjus t the radio se t for fsk operation as 
instructed in paragraph 3-11 a| ,b, c, or d, as applicable 
(OWR or DUPLEX and local or remote). 

c. Adju st the radio se t for am. operation as 
instructed in lparaqraph 3-1 1a , b, c, or d, as applicable. 

3-13. Cw Operation 

For cw operatio n, perf orm th e tuning procedures in 
I paragraphs 3-6 I through l~3^9~l Adjust the receiver in 
accordance with instructions provided in figure 1 1 , TM 
11-5820-358-10 (R-390A/URR); proceed as follows: 

a. Cw Half-Duplex (OWR) Operation from Shelter. 

(1) Connect a key to the MIC or KEY jack on 
the control -unit. (2) Set the control unit SIDETONE 
switch to the receiver (RCVR A or RCVR B) being used. 

NOTE 

The receiver is disabled when transmitting cw. 
(3) Press the key to transmit cw; release the 
key to receive cw. 

b. Cw Duplex Operation from Shelter. 

(1) Perform the procedures indicated in 
subparagraph a (1) and (2) above. 

(2) Tune receiver B as ii j paragraph 3-7.1 1 and 
adjust the receiver according to figure 11, TM 115820- 
358-10 (R-390A/URR). 

(3) Set the transmitter SERVICE SELECTOR 
switch to CW. 

CAUTION 

The receiver is not disabled during transmission. 

(4) The radio set is operational. 

c. Cu, Operation from Remote Site. No provisions 
are made for normal cw operation from the remote site. 
In an emergency, cw operation is possible as follows: 

(1) Adjust the equipment as indicated in 
subparagraph a above. 

(2) Set the control unit TELETYPE switch to 
REMOTE OW. 

(3) Connect the key to the remote site control 
unit CONTROL terminals. (This connection parallels 



TM 11-5820-256-10 

the TTY SWITCH jack and XMTR ON switch of the 
remote control unit.) 

(4) Press the key to transmit. 

3-14. Recognition and Identification of Jamming 

Under real or simulated tactical conditions, the receiver 
may be jammed by the enemy. Jamming is easily 
accomplished by transmitting a strong signal on the 
same frequency, thereby making it difficult or impossible 
to hear the desired signal. Unusual noises or strong 
interference heard on the receive may be enemy 
jamming, signals from a friendly station, noise from a 
local source, or noise caused by a defective receiver. To 
determine whether or not the interference is originating in 
the receiver, disconnect the antenna, remove the 
antenna, or short-circuit the antenna post to the chassis. 
If the interference continues, the receiver is defective. 
Enemy jamming signals may be typed as continuous- 
wave or modulated. 

A jamming signal may be intended to block a single 
frequency. This is called spot jamming. The enemy may 
use one or several transmitters to jam a block or band of 
frequencies. This method is called barrage jamming. 

a. Continuous-Wave Jamming. Cw jamming is 
transmitted as a steady carrier. This signal beats with 
another signal and produces a steady tone in the 
speaker assembly. Cw jamming signals may also be 
keyed by using a random on-and-off signal or using 
actual code characters keyed at the same rate or a little 
faster than the signal being received. 

b. Modulated Jamming. Modulated jamming 
signals may consist of noise, laughter, singing, music, 
various tones, or almost any unusual sound, or they may 
be a combination of these sounds. Various types of 
modulated jamming signals are explained below. 

(1) Spark. This is one of the simplest, most 
effective, and most easily produced jamming signals. 
This type of signal sounds rough, raspy, and sometimes 
like an electric motor with sparking brushes running. 
This signal is broad; therefore, it will interfere with a large 
number of communication channels. 

(2) Sweepthrough. This signal is the result of 
sweeping or moving a carrier back and forth across the 
same frequency at a slow or rapid rate. The numerous 
signals of varying amplitude and frequency produce a 
sound like that of a low-flying airplane passing overhead. 
This type of jamming is effective over a broad range of 
frequencies. When it is varied rapidly, it is effective 
against all types of voice signals. 



Change 4 3-13 



TM 11-5820-256-10 



3) Stepped tones or bagpipes. This signal 
usually consists of several separate tones. The tones 
are transmitted in the order of first increasing and then 
decreasing pitch, repeated over and over. The audible 
effect is similar to the sound of a Scottish bagpipe. 

(4) Noise. Noise is random both in amplitude 
and frequency. It is considered one of the better types of 
jamming modulation. It produces a sound similar to that 
heard when a receiver is not tuned to a station and the 
volume or gain control is turned to maximum. 

(5) Gulls. This signal consists of a quick rise 
and slow fall of a variable audiofrequency. The sound is 
similar to the cry of the sea gull. 

(6) Tone. This signal consists of a single 
audio frequency of varying tone. It produces a steady 
howl in the speaker assembly. Another use of tone is to 
vary it slowly. It produces a howling sound of varying 
pitch. 

3-15. Antijamming 

When it is known that a receiver is being jammed, the 
operator should notify his immediate superior 
immediately and continue to operate the equipment. To 
provide maximum intelligibility of jammed signals, follow 
the operational procedure indicated for each type of 
operation. 

a. When receiving frequency-shift signals, follow 
the procedures in (1) through (9) below in sequence until 
clear copy is printed. 

(1 ) Set the BANDWIDTH KC switch to .1 . 

(2) Adjust the ANT TRIM control for a 
maximum readable output signal. 

(3) If the noise is severe, adjust the LIMITER 

control. 

(4) When the jamming signal is not very 
strong, set the FUNCTION switch to MGC and turn the 
RF GAIN control down. The interfering signal might be 
reduced enough to permit part of the desired signal to 
come through. 

(5) Set the FUNCTION switch to AGC, and try 
different time constants. 

(6) Do not use afc on the converter. 

(7) Try different and more high directional 
antennas. 

(8) If the procedures in (1) through (7) above 
do not provide some degree of signal separation, request 
a change in frequency and call sign. 

(9) If jamming action is such that 
communication is impossible, report this fact to your 
immediate superior. Continue to operate the equipment. 

b. When receiving voice signals and the receiver is 
being jammed, follow the procedures in (1) through (3) 
below in sequence until the signal is heard with the least 
interference. 



(1) Rotate the KILOCYCLES CHANGE 
control slowly through several dial markings on either 
side of the desired signal. Some separation of the 
desired L signal from the jamming signal may be 
achieved. 

(2) Set the BANDWIDTH KC switch to 4 or 2, 
whichever gives the best results. Slowly tune as 
described in (1) above. 

(3) Perform the procedures in a(2) through (5) 
and (7) through (9) above. 

c. If the receive is being jammed when receiving 
cw signals, follow the procedures in (1 ) through (4) below 
in sequence until satisfactory reception is established. 

(1) Rotate the KILOCYCLES CHANGE 
control slowly through a few dial markings on either side 
of the desired signal. Some separation of the desired 
signal from the jamming signal may be achieved. 

(2) Set the BANKWIDTH KC switch to 1 or .1 , 
and set the AUDIO RESPONSE switch to SHARP. 
Slowly tune as described in (1 ) above. 

(3) Reset the BFO PITCH control; it may be 
possible to separate the pitch of the desired signal from 
the jamming signal to provide readability. 

(4) Perform the procedures in A(2) through (5) 
and (7) through (9) above. 

3-16. Stopping Procedure 

The radio set may be disabled by setting the shelter main 
circuit breakers to OFF or by pressing the STOP button 
on the power unit. Use this disabling procedure only as 
an emergency measure, since the individual components 
must be set to their respective off positions before 
restarting. To perform the normal stopping procedure for 
the individual components, set the controls as given in 
the chart below. 



Component Control Position 

Each page printerSEND-LOCK SWITCH.. LOCK 
MOTOR and 

LIGHT switches OFF 

Reperforator LIGHT, MOTOR and 

POWER switches OFF 

Transmitter PLATE RELAY 

switch OFF(down) 

PLATE POWER 

circuit breaker OFF(down) 

Fsk-modulator .... POWER switch OFF(down) 

Matching unit SELECTOR switch POWER 

METER ADJUST 

control Full ccw 

Control Unit BIAS POWER switch .... OFF 

AC POWER switch OFF(down) 

Converter POWER switch OFF(down) 

Each receiver FUNCTION switch OFF 



Change 4 3-14 



TM 11-5820-256-10 

Component Control Position 



Speaker assembly CHANNEL A and 

B switches OFF(down) 

Blower assembly. Power switch OFF(down) 

Transmitter FILAMENT POWER 

circuit breaker OFF(down) 

Shelter Circuit breakers OFF 

Power Unit Circuit breaker OFF 

START-STOP switch PRESS TO STOP 



Change 4 3-15 



TM 11-5820-256-10 



CHAPTER 4 
MAINTENANCE INSTRUCTIONS 



4-1. Scope of Operator's Maintenance 

The maintenance duties assigned to the operator of 
Radio Set AN/GRC-26D are listed below, together with a 
reference to the paragraphs covering the specific 
maintenance function. The duties do not require tools or 
test equipment other than those issued with the set. 

a. Daily pre ventive maintenance checks and 
services |(para 4-51 . 

b. Weekly p reventive maintenance checks and 
services fTpara 4-61 

c. Cleaninq Rpara 4-7). 

d. Lubrication Kpara 4-8) . 

e. Maintenance checks Rpara 4-9> . 

f. Replacement of defective fu ses! (para 2-7( 1 . 

g. Checking cable connection s! (para 2 : 9) . 

4-2. Tools Required for Maintenance 

The tools required for maintenance are l isted i n |appendix| 
[land illustrated in figures B-1, B-2, andlfidjll 

4-3. Preventive Maintenance 

Preventive maintenance is the systematic care, 
servicing, and inspection of equipment to prevent the 
occurrence of trouble, to reduce downtime, and to assure 
that the equipment is serviceable. 

a. Systemat ic Care. Th e procedures given in 
I paragraphs 4-1 I through I 4-9 I cover systematic care 

essential to proper upkeep and operation of the 
equipment. The cleaning operations ! (para 4-7) should 
be performed once a day. If the equipment is not used 
daily, however, the cleaning operations must be 
performed before operation after any extended 
shutdown, or once a week while the equipment is kept in 
standby condition. 

b. Maintenance Service and Ins pection. The 
mai ntenance checks and services charts Kpara 4-5l and 

1 4-61 outline inspections to be made at specific intervals. 
These inspections are made to determine that the 
equipment is in good general (physical) condition, in 
good operating condition, and likely to remain combat 



serviceable. To assist operators in maintaining combat 
serviceability, the charts indicate what to inspect, how to 
inspect, and what the normal conditions are; the 
References column lists the paragraph or illustrations 
that contain additional information. If the defect cannot 
be remedied by the operator, higher category 
maintenance or repair is required. 
Records and reports of these inspections must be made 
in accordance with TM 38750. 

4-4. Maintenance Checks and Services Periods 

Maintenance checks and services of the AN/ GRC-26D 
are re quired on a daily a nd weekly basis. 

a. I Paragraph 4-5 I specifies checks and services 
that must be accomplished daily and under the special 
conditions listed below: 

(1) Vehicular installation. 

(a) Before the vehicle starts on a 

mission. 

(b) When the equipment is initially 

installed. 

(c) When the equipment is reinstalled 
after removal for any reason. 

(d) At least once each week if the 
equipment is maintained in standby condition. 

(2) Transportable and mobile installations. 

(a) When the equipment is initially 

installed. 

(b) When the equipment is reinstalled 
after removal for any reason. 

(c) At least once a week if the 
equip ment is maintained in standby condition. 

b. l Paragraph 4-6 1 specifies maintenance checks 
and services that must be performed once each week. If 
the equipment is being ma intained in a standby 
condition, the daily fpara 4-51 and weekly Kpara 4-6) 
checks and services should be accomplished at the 
same time. 



4-1 



TM 11-5820-256-10 



4-5. Daily Preventive Maintenance Checks and Services Chart 

Sequence 

No. Item to be Inspected Procedure 

1 Completeness Inspect equipment for completeness 

2 Installation Inspect equipment for proper in- 

stallation. 

3 Cleanliness Units must be clean and dry inside 

and out and free of dirt, grease, 
corrosion, and fungus. 

4 Cables All cables must be free of cuts, 

cracked or gouged jackets, 
fraying, or kinks. 

5 Meters Meters must be free of chips and 

cracks. Indicator should be straight 
and move freely. 

6 Antenna Insulators are free of cracks, dirt, 

and fungus. Mast sections are not 
bent. Guy wires and transmission 
lines are not kinked and do not 
show signs of fraying. 

7 Hardware Catches, hinges, latches, and handles 

must be in good condition without 
broken or missing components. 

8 Plugs and receptacles Plugs and receptacles shall be firmly 

seated and free from chips and 
breaks. 

9 Controls Controls should move freely without 

binding. Knobs must be tight on 
the shafts. 

1 Operating check Check the radio set for proper 

operation 



Reference 

Appx B. 

I Para 2-1l throuah f^TO1 

I Para 4-71 



I Fig. 2-7115^1 andE3 



I Para S-Sl throuah rS^ and fmi 



4-6. Weekly Preventive Maintenance Checks and Services Chart 

Sequence 

No. Item to be Inspected Procedure Reference 

1 Interlocks Inspect for evidence of failure 

2 Knobs, dials, and switches Check for proper mechanical action by 

setting each control to each of its 
settings. 

3 Mountings Inspect seating and stability of mount- 

ings. Check for loose or missing 
hardware. 

4 Canvas and leather Check to see that items are free from 

mildew, tears, and fraying. 

5 Air filters Check to see that air filters are clean. 

6 Storage batteries Check to see that batteries are free 

from dirt, corrosion, and leakage. 

7 Shelter Shelter must be in good condition and 

free from leaks. Weatherproofing 
must be in good condition. 



4-7. Cleaning 

Inspect the exteriors of the units within the shelter. The 
exterior surfaces should be clean and free of dirt, 
grease, and fungus. 

a. Remove dust and other loose dirt with a clean, soft 
cloth. 

WARNING 
Prolonged breathing of cleaning 
compound is dangerous; make 
certain that adequate ventilation is 



provided. Cleaning compound is 
flammable; do not use near a flame. 
Avoid contact with the skin; wash off 
any that spills on the hands. 

b. Remove grease, fungus, and ground-in dirt from 
the cases; use a cloth dampened-(not wet) with Cleaning 
Compound (FSN 793043959542). 

c. Remove dirt from plugs and jacks with a brush. 



4-2 



CAUTION 

Do not press on the meter faces 
(glass) when cleaning; the meter may 
be damaged. 

d. Clean the front panels and control knobs; use a 
soft, clean cloth. If dirt is difficult to remove, dampen the 
cloth with water; mild soap may be used to make the 
cleaning more effective. 

4-8. Lubrication Instructions 

a. General. 

(1) The type of lubricant to be used, the 
interval, and the specific instructions for each component 
of the radio set are given in their respective technical 
manuals (appx A). Lubrication for the shelter ventilator 
blower is given in b below. 

(2) Apply Lubricating Oil, General Purpose 
(FSN 9150-185-0629) (FED VV-I800) sparingly to 
springs and loops of all helical springs, to prevent wear 
and rust. 

b. Shelter Ventilating Blower Kfig. 1-9)1 Lubricate 
the shelter ventilating blower with Lubricating Oil, Engine 
(FSN 9150-265-9425) (MILL2104). Oilcups are located 
at each end of the motor. 

c. Mechanical Devices of Shelter. Lubricate all 
movable parts of the shelter, such as hinges, latches, 
etc, with a light coat of oil (MIL-L2104) to insure against 
rust and corrosion and to provide for better operation. 
Wipe off excess lubricant to prevent contamination by 
dirt. 

d. Raceways of Cabinet. The raceways of cabinets 
should be lubricated with oil (FED VVL-800) to assure 
easy removal of chassis for repairs. 



TM 11-5820-256-10 

4-9. Maintenance Checks 

When the equipment fails to perform properly, remove 
power from the radio set and make the checks listed in a 
through d below. If this fails to correct the trouble, repeat 
the starting a nd tuning procedures described in 

I paragraphs 3-6I throuah l 3-8,1 and re peat the applicable 
operating pro cedure described in I paragraphs 3-101 

I through 3-13.1 If a page printer or a receiver appears to 
be in trouble, the second page printer or receiver, as 
applicable, may be substituted as described in e and f 
below. The transmitter may be checked as described in 
g below. If these procedures fail to correct the trouble, 
note the specific trouble symptom and notify the 
supporting maintenance organization. 

a. Improperly connected or loose cables and plugs 
Kpara 2-9a and c). 

b. Poor ground connections lfpara 2-"9) . 

c. Ground ed or broken antennas or antenna lead-in 
wires [para 2-9a and c). 

d. Burned-out fuses ffoara 2-7t . 

e. If a page printer is defective and one-way 
reversible operation is being used, the second page 
printer may be substituted for the one in trouble by 
disconnecting the cables at the control unit and 
connecting the identical cables from the second page 
printer in their place. 

f. If the A-receiver is suspected of being in trouble, 
tune the B- receiver as described in l paragraphs 3-61 

I through 3-8H and set the SIDETONE and REMOTE TEL 
switches on the control unit to REC B. 

g. The transmitter may be checked by setting the 
control switch on the matching unit to POWER. 



4-3 



TM 11-5820-256-10 

CHAPTER 5 

SHIPMENT AND LIMITED STORAGE AND DEMOLITION 
TO PREVENT ENEMY USE 



Section I. SHIPMENT 

5-1. Disassembly of Equipment 

The following instructions are recommended as a guide 
for preparing the radio set for transportation and storage. 

a. Disconnect any outside field wire lines. 
Disconnect the power cable from the power unit. 

b. Roll up the power cables, and store them in the 
shelter. 

c. Take down the doublet antennas, if used; 
disconnect the coaxial cables. Repack the antennas, 
and replace the cables on the reel. 

d. Disassemble the whip antennas if mobile 
operation is not anticipated. Store the antennas in the 
shelter. 

e. Disconnect the grounding wire, and remove the 
ground rod. Store the wire and ground rod in the shelter. 

f. Cover the page printers and reperforator with the 
canvas covers. 

g. Make sure that all components are mounted 
securely and fastened tightly. 



LIMITED STORAGE 

h. Store all loose items, such as the microphone, 
key, and technical manuals, in the compartments of the 
storage cabinet. 

i. Pack empty spaces in the storage cabinet to 
prevent shifting of contents. Close the cabinet drawers 
securely. 

j. Close all windows, the roof hatch, and the 
feedthrough holes in the shelter. 

k. Store the coaxial cables and reels, antenna mast 
equipment, power cables, and antenna wires in the 
shelter to prevent loss if the power unit trailer becomes 
separated from the shelter. Secure all these 
components to prevent shifting during transportation. 

5-2. Repackaging for Shipment or Limited Storage 

Repackaging a Radio Set AN/GRC-26D is performed at 
a higher maintenance category. 



Section II. DEMOLITION OF MATERIEL TO PREVENT ENEMY USE 



5-3. Authority for Demolition 

Demolition of the equipment will be accomplished only 
upon the order of the commander. The destruction 
procedures outlined in I paragraph 5-4 I will be used to 
prevent further use of the equipment. 

5-4. Methods of Destruction 

Use any of the following methods to destroy the 
equipment: 

a. Smash. Smash the controls, tubes, coils, 
switches, capacitors, transformers, and meters; use 
sledges, axes, handaxes, pickaxes, hammers, or 
crowbars. 

b. Cut. Cut all the interconnecting cables and 
power cables; use axes, handaxes, or machetes. 



WARNING 
Be careful when using explosives 
and incendiary devices. Do not use 
these items unless the need is 
extremely urgent. 

c. Burn. Pack rags, clothing, or canvas under and 
around the components. Saturate this packing with 
gasoline, oil, or diesel fuel and ignite it. Burn cables and 
technical manuals; use gasoline, kerosene, oil, flame- 
throwers, or incendiary grenades. 

d. Bend. Bend all panels and cabinets. 

e. Explode. If explosives are necessary, use 
firearms, grenades, TNT, or artillery. 

f. Dispose. Bury or scatter the destroyed parts in 
slit trenches or foxholes, or throw them into streams. 



5-1 



TM 11-5820-256-10 

Figure 5-1. Shelter, Electrical Equipment S-56(*)/U, interunit cabling. 
(Located in back of manual) 



5-3 



TM 11-5820-256-10 



Figure 5-2. Shelter, Electrical Equipment S-6(*)/U, interunit cabling (modified 
per MWO 1 1 148S-564-5/1 ). 

(Located in back of manual) 



5-5 



TM 11-5820-256-10 



APPENDIX A 
REFERENCES 



Following is a list of applicable references that should be available to the operator of Radio Set AN/GRC-26D: 

DA Pam 31 0-4 Index of Technical Manuals, Technical Bulletins, Supply Manuals (types 7,8,' 

and 9), Supply Bulletins and Lubrication Orders. 
DA Pam 31 0-7 U.S. Army Equipment Index of Modification Work Orders. 

MWO 1 1 -5820-256-35/1 Modification of Radio Set AN/GRC-26D to Provide Communication Security 

Facilities in Shelters S-56/G, S-56A/G, and S-56B/G. 
SB 1 1 -544 Limited Usage of Mast AB-1 55/U With Radio Beacon Set AN/GRN-6 

Pending Redesign of Mast AB-360/G. 
TB SIG 272 Microphone M-29A/U and M-29B/U. 

TB SIG 291 Safety Measures To Be Observed When Installing and Using Whip Antennas, 

Field Type Masts, Towers, Antennas, and Metal Poles That Are 
Used With Communication, Radar, and Direction Finder Equipment. 

TM 5-2805-259-14 Operator, Organizational, Direct Support, and General Support Mainte- 

nance Manual: Engine, Gasoline, 20 HP; Military Standard Models; 
(Model 4A084-2) (NSN 2805-00-925-3926 and (Model 4A084-3) (NSN 2805 
00872-5972). 

TM 5-6115-275-14 Operator, Organizational, Intermediate (Field), (Direct Support and General 

Support), and Depot Maintenance; Generator Set, Gasoline Engine Driv- 
en, Skid Mounted, Tubular Frame, 10 KW, AC, 120/208 V, 3 Phase: and 
120/240 V Single Phase-Less Engine; DOD Model MEP-018A, 60 Hz 
(NSN 61 1 5-00-889-1 447) and DOD Model MEP-023A, 400 Hz (NSN 61 1 5-00- 
926-0843). 

TM 1 1 -337 Telephone Sets TA-43/PT and TA-263/PT. 

TM 11-809-10 Operator's Manual: Radio Transmitters T-368/URT, T-368A/URT, T- 

368B/URT, T-368C/URT, T-368D/URT, and T-368E/URT, Antenna, Tun- 
ing Unit BC-939B; Radio Frequency Tuner TN-339/GR; and Standing 
Wave Ratio-Power Meter ME-165/G. 

TM 11-826 Radio Transmitters BC-610-E, -F, -G, -I and Radio Transmitter, T- 213/GRC- 

26, and Antenna Tuning Units BC-939-A and -B. 

TM 1 1 -2241 Frequency Shift Converters CV-1 1 6/URR, CV-1 1 6A/URR, CV-1 1 6B/URR 

and CV-1 16C/URR. 

TM 1 1-3895-201 -13P Operator, Organizational, and Field (Third Echelon) Maintenance Repair 

Parts and Special Tool Lists and Maintenance Allocation Chart: Axles 
RL-27-B, RL-27-C, and RL27-D 

TM 1 1 -41 40-200-1 OP Operator's Repair Parts and Special Tools List: Blower Assembly, Electri- 
cal HD-223/G. 

TM 1 1 -541 0-200-20P Organizational Maintenance Repair Parts and Special Tools Lists; Shelters 

S-56/G, S-56A/G, and S-56B/G (FSN 5410-132-6679). 

TM 1 1 -5805-201 -1 2 Operator and Organizational Maintenance Manual, Including Repair Parts 

and Special Tool Lists; Telephone Set TA-31 2/PT. 

TM 1 15805-256-24P Organizational, Direct Support, and General Support Maintenance Repair 

Parts and Special Tools Lists (Including Depot Maintenance Repair Parts 
and Special Tools): Telephone Set TA-43/PT (FSN 5805503-2775). 

TM 1 1 -581 5-200-1 2 Operator's and Organizational Maintenance Manual Including Repair Parts 

and Special Tools List; Teletypewriter Sets AN/FGC-20, AN/FGC-20X, 
AN/FGC-21 , AN/FGC-66, AN/FGC-159, AN/FGC-159X, AN/FGC-160, 
AN/FGC-177, AN/UGC-4, AN/UGC-29, AN/UGC-29X and Teleprinter 
TT-259/FG. 



Change 4 A-1 



TM 11-5820-256-10 



TM 


11 


-5820-321-1 OP 


TM 


11 


-5820-357-1 


TM 


11 


-5820-358-1 


TM 


11 


-5820-359-1 2P 


TM 


11 


-5820479-1 2P 



TM 1 1 -581 5-238-1 2 Operator's and Organizational Maintenance Manual Including Repair Parts 

and Special Tools List; Teletypewriter Sets AN/GGC-3 and AN/GGC-3A, 
AN/GGC-53 and AN/GGC-53A, and Teletypewriter Reperforator-Transmitters 
TT-76/GGC, TT-76A/GGC, TT-76B/GGC, TT-76C/GGC, TT- 
699/GGC, TT-699A/GGC, TT-669B/GGC, TT-699C/GGC. 
TM 1 1 -5820-251 - 1 4P Operator's Organizational, Direct Support, and General Support Maintenance 

Repair Parts and Special Tools List (Including Depot Maintenance 
Repair Parts and Special Tools): Masts AB-155/U (FSN 5820-251-2366), 
AB-155A/U (FSN 5985-507-6261), and AB-155B/U (FSN 5985-732-5146). 
TM 1 1 -5820-257-1 2P Operator and Organizational Maintenance Repair Parts and Special Tool 

Lists and Maintenance Allocation Chart: Antenna Tuning Units BC-939-A 
and BC-939-B and Tuner, Radio Frequency TN-339/GR. 
Operator's Maintenance Repair Parts and Special Tools List: Modulators, 

Radio MD-239/GR and MD-239A/GR. 
Operator's Manual: Radio Receiver R-390/URR. 
Operator's Manual: Radio Receiver R-390A/URR. 
Operator and Organizational Maintenance Repair Parts and Special Tool. 

Lists and Maintenance Allocation Chart: Power Supply PP-621/URR. 
Operator and Organizational Maintenance Repair Parts and Special Tools 
List and Maintenance Allocation Chart: Mast Base MP-65, MP-65A and 
MP-65B. 

TM 1 1 -5930-201 -1 4P Operator's Organizational, Direct Support, and General Support Maintenance 

Repair Parts and Special Tools Lists (Including Depot Maintenance 
Repair Parts and Special Tools); Switch Box SA-331/U (FSN 5930-548-6806). 

TM 1 1 -5965-201 -1 4P Operator's, Organizational, Direct Support, and General Support Maintenance 

Repair Parts and Special Tools Lists (Including Depot Maintenance 
Repair Parts and Special Tools) Loudspeaker Assemblies LS-206/U and 
LS-206A/U (FSN 5965-347-0231). 

TM 1 1 -5965-224-1 4P Operator's, Organizational, Direct Support and General Support Maintenance 

Repair Parts and Special Tools Lists (Including Depot Maintenance 
Repair Parts and Special Tools): Handsets H-60/PT (FSN 5965-669-9145) 
and H-165/U (FSN 5965-543-1837). 

TM 1 1 -5965-231 -1 4P Operator's, Organizational, Direct Support, and General Support Maintenance 

Repair Parts and Special Tools Lists (Including Depot Maintenance 
Repair Parts and Special Tools): Headset, Electrical H-1 13/U (FSN 5965- 
504-6370). 

TM 1 1 -6625-333-1 5 Operator's, Organizational, DS, GS, and Depot Maintenance Manual Including 

Repair Parts and Special Tools List; Standing-Wave-Ratio Power 
Meter ME-165/G. 

TM 38-750 The Army Maintenance Management System (TAMMS). 

TM 740-90-1 Administrative Storage of Equipment. 

TM 750-244-2 Procedures for Destruction of Electronics Material to Prevent Enemy Use 

(Electronics Command). 

SB 708-42 Federal Supply Code for Manufacturers; United States and Canada - Code 

to Name (Cataloging Handbook H4-2). 



Change 4 A-2 



TM 11-5820-256-10 

APPENDIX B 

BASIC ISSUE ITEMS LIST (BIIL) AND ITEMS TROOP 
INSTALLED OR AUTHORIZED LIST (ITIAL) 



Section I. INTRODUCTION 



B-1. Scope 

This appendix lists only basic issue items required by the 
crew/operator for installation, operation, and 
maintenance of Radio Set AN/GRC-26D. 

B-2. General 

This Basic Issue Items and Items Troop Installed or 
Authorized List is divided into th e following se ctions: 

a. Basic Issue Items List l-Section II. I A list, in 
alphabetical sequence, of items which are furnished with, 
and which must be turned in with the end item. 
b. Items Troo p Installed or Authorized List lSectioTil 

nrnsa JsictioTriTTi 

B-3. Explanation of Columns 

The following provides an explanation of columns found 
in the tabular listings: 

a. Illustration. This column is divided as follows: 

(1) Figure Number. Indicates the figure 
number of the illustration in which the item is shown. 

(2) Item Number. Not applicable. 

b. Federal Stock Number. Indicates the Federal 
stock number assigned to the item and will be used for 
requisitioning purposes. 

c. Part Number. Indicates the primary number 
used by the manufacturer (individual, company, firm, 
corporation, or Government activity), which controls the 
design and characteristics of the item by means of its 
engineering drawings, specifications standards, and 
inspection requirements, to identify an item or range of 
items. 



d. Federal Supply Code for Manufacturer (FSCM). 
The FSCM is a 5-digit numeric code used to identify the 
manufacturer, distributor, or Government agency, etc, 
and is identified in SB 08-42. 

e. Description. Indicates the Federal item name 
and a minimum description required to identify the item. 

f. Unit of Measure (U/M). Indicates the standard of 
basic quantity of the listed item as used in performing 
the actual maintenance function. This measure is 
expressed by a two-character alphabetical abbreviation, 
(e.g., ea, in., pi, etc). When the unit of measure differs 
from the unit of issue, the lowest unit of issue that will 
satisfy the required units of measure will be 
requisitioned. 

g. Quantity Furnished with Equipment (Basic Issue 
Items Only). Indicates the quantity of the basic issue 
item furnished with the equipment. 

h. Quantity Authorized (Items Troop Installed or 
Authorized Only). Indicates the quantity of the item 
authorized to be used with the equipment. 

B-4. Special Information 

Usable on codes are included in Column 5. Uncoded 
items are applicable to all models. Identification of the 
usable on codes are as follows: 

Code Used on 

1 AN/GRC-26D 

2 AN/GRC-26D with MWO 



Change 1 B-1 



TM 11-5820-256-10 



Section II. BASIC ISSUE ITEMS LIST 



(1) 


(2) 


(3) 


(4) 


(5) 




(6) 


(7) 


Illustration 


Federal 










Unit 


Qty 






stock 


Part 


FSCM 


Description 




of 


turn 


(A) 


(B) 


number 


number 




Usable 




meas 


with 


Fiv 

1 1 A 


1 to m 

1 ICI 1 1 








on code 






equip 


No 


No 
















IB-41 




5340-260-1314 


MC 92 




Padlock 


1 


EA 


1 


B-111 




5975-511-8658 


SC-B-75592A 


80063 


Rod Ground 


1 


EA 


1 


B^T 


5 


5815-348-2137 






Cabinet Storage, CY-1721/GRC; 


1 


EA 


1 












CY-1721A/GRC 








|B-7| 


4 


2540-892-6243 






Ladder, Vehicle, Boarding MX-3391/G 


1 


EA 


1 


B-1 


1 


6230-239-3518 




81349 


Light Extension: (25 Ft) 12293 


1 


EA 


1 


^5l 




7110-082-6109 






Cabinet, Filing, Security: HAF-358C 




EA 


1 


B^9| 


2 


5820-497-8792 


SC-B-27964 


80063 


Strap, Webbing 


1 


EA 


1 


B-141 




5820-576-5379 


SC-C-19825 


80063 


Strap, Webbing 


1 


EA 


1 


r^7i 


3 


5815-813-9768 


SC-C-19825A 


80063 


Strap, Webbing 




EA 




B-141 


4 


5815-579-6007 


SC-D-19825B 


80063 


Strap, Mounting 




EA 




_M 




6645-303-4950 




36922 


Clock, Aircraft, Mechanical: All 




EA 




eT3| 


3 


7920-663-3240 






Broom, Upright 




EA 




B-1 3| 


2 


7110-273-3962 




24052 


Chair, Rotary: 2123 




EA 




B-1 31 




7105-514-5090 






Chair, Folding 




EA 




B-1 Ol 


1 


7520-254-4610 






Clip Board, File 




EA 





Section III. ITEMS TROOP INSTALLED OR AUTHORIZED LIST 



(1) 


(2) 


(3) 




(4) 


(5) 




Federal 




Usable 


Unit 




SMR 


stock 


Description 


on 


of 


Qty 


CODE 


number 


Reference Number & Mfr. Code 


code 


meas. 


auth. 




5120-223-7013 


Wrench, socket; SC-C-28016;80063 


1 


EA 


1 



Change 1 B-2 




B-3 



TM 11-5820-256-10 




TM 11-5820-256-10 






B-10 



TM 11-5820-256-10 




Figure B-9. 



B-11 



TM 11-5820-256-10 




Figure B-10. 
B-12 



TM 11-5820-256-10 




Figure B-12. 



B-13 



TM 11-5820-256-10 




Figure B-13. 



B-14 



TM 11-5820-256-10 




Figure B-16. 
B-16 



INDEX 



TM 11-5820-256-10 



Accessories, operating 

Adjustments, initial 

Am. voice operation 

Antennas: 

Doublet and Mast AB-1 56(*)/U 

Whip 

Antijamming 

Assembly, Loudspeaker LS-206(*)/U 

Authority, demolition 

Blower Assembly, Electrical HD-223/G: 

Controls 

Description 

C-1123/GRC 

C-1474/GRC 

Cabinet, Electrical Equipment CY-1807/G description 

Cabinet, Storage CY1 721 (*)/GRC description 

Checking unpacked equipment 

Cleaning 

Clock, description 

Components, nonoperating 

Connections 

Control, Radio Set C-1 123/GRC 

Control, Remote Switching C-1474/GRC 

Controls, indicators, and jacks: 

C-1 123/GRC 

MD-239(*)/GR 

Minor components 

Converter, Frequency Shift CV-416(*)/URR 

CV-1 16(*)/URR 

Cw operation 

Daily preventive maintenance checks and services chart 

Destruction, methods 

Differences, models 

Disassembly, equipment 

Doublet antennas 

Forms and records 

Frequency Shift Converter CV-116(*)/.URR 

Fsk-am. operation 

Fsk operation 

Fuses and batteries, installation 

Generator Set, Gasoline Engine, Trailer Mounted PU-474/M. 
Generator Set, Gasoline Engine, Trailer Mounted PU-294/G . 

Heater 

Indexes, publications 

Indicators, controls, and jacks: 

C-1 123/GRC 

MD-239 (*)/GR 

Initial adjustments 

Installation: 

Doublet antennas and Mast AB-1 55(*)/U 

Fuses and batteries 

Operator's chairs 

Shelter, Electrical Equipment S-56(*)/G 

Whip antenna 

Interconnection Box J-224/GRC 



Paragraph 


Page 


1-28 


1-7 


?-i n 


?-9 


3-11 


3-11 


2-6, 1-26 


2-3, 1-6 


2-5 


2-2 


3-15 


3-13 


1-15 


1-5 


5-3 


5-1 


3-4 


3-3 


1-9 


1-4 


1-10, 3-2 


1-4, 3-1 


1-21 


1-6 


1-29 


1-7 


1 -29 


1 -7 


2-3 


2-2 


4-7 


4-2 


1-29 


1-7 


1-29 


1-7 


2-9 


2-8 


1-10 


1-4 


1-21, 3-4 


1-6, 3-3 


3-3 


3-1 


3-2 


3-1 


3-4 


3-3 


1-11 


1-4 


1-11 


1-4 


3-13 


3-12 


4-5 


4-2 


5-4 


5-1 


1-28 


1-7 


5-1 


5-1 


2-6, 1-26 


2-3, 1-6 


1-3 


1-1 


1-11 
i i i 


1 -A 


3-12 


3-11 


3-10 


3-10 


2-7 


2-7 


1 -?7 

I <— 1 


1 -7 

I / 


1-26 


1-6 


1-24 


1-6 


1-2 


1-1 


3-3 


3-1 


3-2 


3-1 


2-10 


2-9 


2-6 


2-3 


2-7 


2-7 


2-8 


2-8 


2-4 


2-2 


2-5 


2-2 


1-23 


1-6 



1-1 



TM 11-5820-256-10 



Paragraph Page 

Interconnection Box J-2623/GRC 1-22 1-6 

Junction Box J-2598/GRC 1-25 1-6 

Junction Box J-2597/GRC 1-24 1-6 

Key, Telegraph KY-1 1 6/U 1 -28 1 -7 

Lubrication instructions 4-8 4-3 

Loudspeaker Assembly LS-206(*)/U 1-15 1-5 

Maintenance: 

Checks 4-9 4-8 

Checks and services periods 4-4 4-1 

Preventive, checks and services charts 4-5, 4-6 4-2 

Mast AB-155(*)/U 2-6 2-3 

ME-165/G 1-18 1-6 

MD-239Q/GR 1-16 1-5 

Models, differences 1-28 1-7 

Modulator, Radio MD39(*)/GR 1-16 1-5 

Nomenclature and common names 1-6 1-3 

Nonoperating components 1-29 1-7 

Operating: 

Accessories 1-28 1-7 

Conditions 3-9 3-10 

Operation: 

Am. voice 3-11 3-11 

Cw 3-13 3-12 

Fsk 3-10 3-10 

Fsk-am 3-14 3-12 

Types 3-5 3-7 

Operator's controls and indicators: 3-1 3-1 

C-1123/GRC 3-3 3-1 

MD-239(*)/GR 3-2 3-1 

Minor components 3-4 3-3 

Preliminary starting procedure 3-6 3-7 

Preventive maintenance: 4-3 4-1 

Checks and services: 

Charts 4-5,4-6 4-2 

Periods 4-4 4-1 

Procedures: 

Preliminary starting 3-6 3-7 

Starting 3-7 3-8 

Stopping 3-16 3-13 

Tuning 3-8 3-8 

PU474/M 1-25 1-6 

PU-294/G 1-24 1-6 

Purpose and use 1-4 1-2 

R-S90/*)/URR 1-12 1-5 

Radio Set AN/GRC-26D 1-7 1-3 

Radio Transmitter T368(*)/URT 1-17 1-6 

Receiver, Radio R4390(*)/URR 1-12 1-5 

Recognition and identification, jamming 3-14 3-12 

Repackaging, shipment or limited storage 5-2 5-1 

Reperforator-Transmitter, Teletypewriter TT-76(*)/GGC 1-13 1-5 

Scope: 

Manual 1-1 1-1 

Operator's maintenance 4-1 4-4 

Shelter, Electrical Equipment S-56(*)/G 1-8 1-3 

Siting 2-1 2-1 

Standing Wave Ratio-Power Meter ME-1 65/G 1-18 1-6 

Starting procedure 3-7 3-8 

Stopping procedure 3-16 3-13 

Switch Box SA-331 /U 1-28 1-7 

Technical characteristics 1-5 1-2 

Telephone Set TA-312/PT 1-20 1-6 

Teletypewriter TT-98(*)/FG 1-14 1-5 

TN-339/GR 1-19 1-6 



I-2 



TM 11-5820-256-10 



Paragraph Page 

Tools required, maintenance 4-2 4-1 

Transmitter, Radio T-668(*)/URT 1-17 1-6 

TT-980/FG 1-14 1-5 

TT-760/GGC 1-13 1-5 

Tuner, Radio Frequency TN-389/GR 1-19 1-6 

Tuning procedure 3-8 3-8 

Unpacking 2-2 2-1 

Weekly preventive maintenance checks and services chart 4-6 4-2 

Whip antenna: 

Description 1-28 1-7 

Installation 2-5 2-2 



I-3 



By Order of the Secretary of the Army 



Official: 

KENNETH O., WICKHAM 

Major General, United States Army, 
The Adjutant General. 

Distribution: 

To be distributed in accordance with DA Form 12-51 , (qty rqr block no. 97) Operator maintenance requirements for 
AN/GRC-26 Radio Set. 

AU.S GOVERNMENT PRINTING OFFICE: 1995 - 388-421/41096 



TM 11-5820-256-10 

W.C. WESTMORELAND, 
General, United States Army, 
Chief of Staff. 



THE METRIC SYSTEM AND EQUIVALENTS 



LINEAR MEASURE 

1 Centimeter ~ 10 Millimeters = 0.0 1 Meters = 

0.3937 Inches 
1 Meter = 100 Centimeters - 1.000 Millimeters = 

39.37 Inches 
I Kilometer: 1.000 Meters: 0.621 Miles 
SQUARE MEASURE 

/ Sq Centimeter = 100 Si) Millimeters = 0. 1 55 Sit Inches 
I Sq Meter = 10.000 Sq Centimeters = 10.76 Sq K-cl 
I Sq Kilometer - 1.000.000 Sq Meters = 0.386 Sq Miles 
CUBIC MEASURE 

I Cu Centimeter = 1.000 Cu Millimcicrs = 0.06 ( u Inches 
1 Cu Meter = 1.000.000 Cu Centimeters : 35.31 Cu K'ct 



■ 0.033K Huid Ounces 
33.82 Huid Ounces 



LIQUID MEASURE 

I Milliliter = 0.001 I Hers : 
1 I. iter : 1.000 Milliters : 
TEMPERATURE 

5/9 -32) = °C 

212° hahrenhcit is equi\alcnt to 100' Celsius 
90° Kahrenheit is equivalent to 32 2 C Celsius 
32° l-ahrcnheit is equivalent to 0'- Celsius 
9/5 C c -32 = Y~- 
WEIGHTS 

I Gram = 0001 Kilograms = 1.000 Milligrams = 

0.035 Ounces 
I Kilogram = 1.000 Grams = 2.2 I h. 
I Metric 1 on = 1.000 Kilograms = I Mcgagram - 

I I Short I ons 



APPROXIMATE CONVERSION FACTORS 



TO CHANGE 

Inches 

l-ect 

Yards 

Miles 



TO 

Centimeters 
Meters 
Meters 
Kilometers . 



Square Inches Square Centimeters 

Square l-cct Square Meiers 

Square Yards Square Meiers 

Square Miles Square Kilometers 

Acres Square Hectometers 

Cubic heel Cubic Meiers 

Cubic Yards Cubic Meters 

Huid Ounces Milliliters 

Pints I iters 

Quarts I iters 

Gallons I iters 

Ounces (irams 

Pounds Kilograms 

Short Tons Metric Ions 

Pound-feel Newton-Meters 

Pounds Per Square Inch .... KilopascaK 

Miles Per Gallon Kilometers Per I iter . . . 

Miles Per Hour Kilometers Per Hour ... 

TO CHANGE TO 

Centimeters Inches 

Meters l-cet 

Meters Yards 

Kilometers Miles 

Square Centimeters Square Inches 

Square Meters Square l-eet 

Square Meters Square Yards 

Square Kilometers Square Miles 

Square Hectometers Acres 

Cubic Meters Cubic l-ect 

Cubic Meters Cubic Yards 

Milliliters Huid Ounces 

Liters Pints 

Liters Quarts 

Liters Gallons 

Grims Ounces 

Kilograms Pounds 

Metric Tons Short Tons 

Newton-Meiers Pound-Keet 

Kilopascals Pounds Per Square Inch 

Kilometers Per Liter Miles Per Ga lion 

Kilometers Per Hour Miles Per Hour 



MULTIPLY BY 

2. 54(1 

305 
0.914 

1 6(19 
6.451 
093 
0.K36 
2.59(1 
0.405 
02K 
0.765 

29.573 
473 

946 
3.7H5 

28 349 
0454 
0907 
1.356 
6 895 
0425 

1 609 
MULTIPLY BY 

394 
3.2KO 

1 094 
621 
155 

10.764 
1.196 
0.3X6 

2 471 
35.315 

1.308 
0.034 
2.113 
1.057 
0.264 
0035 
2.205 
1.102 
0.738 
145 
2 354 
0.621 



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